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BLUEPRINT READING 



A PRACTICAL MANUAL OF INSTRUCTION IN BLUEPRINT READ- 
ING THROUGH THE ANALYSIS OF TYPICAL PLATES WITH 
REFERENCE TO MECHANICAL DRAWING CON- 
VENTIONS AND METHODS, THE LAWS OF 
PROJECTION, ETC. 



BLUEPRINT READING 
By HOWARD P. FAIRFIELD 



POLYTECHNIC INSTITUTE; AMERICAN SOCIETY OF 
MECHANICAL ENGINEERS 



MECHANICAL DRAWING 
By ERVIN KENISON, S.B. 

ASSOCIATE PROFESSOR OF DRAWING AND DESCRIPTIVE GEOMETRY, 
MASSACHUSETTS INSTITUTE OF TECHNOLOGY 

And EDWARD B. WAITE 

FORMERLY DEAN AND HEAD, CONSULTING DEPARTMENT, AMERICAN 

SCHOOL OF CORRESPONDENCE; AMERICAN SOCIETY OF 

MECHANICAL ENGINEERS 



ILLUSTRATED 



AMERICAN TECHNICAL SOCIETY 
CHICAGO 

1919 






COPYRIGHT, 1919, BT 

AMERICAN TECHNICAL SOCIETY 



COPYRIGHTED IX GREAT BRITAIN- 
ALL RIGHTS RESERVED 



©CIA511829 



INTRODUCTION 

BLUEPRINTS are the language by which a designer expresses 
his thoughts to the fabricator. They may represent some 
complicated machine which will be made in fifty separate pieces 
and will go together like a jig puzzle; they may represent the 
specifications for a big bridge or roof truss which will guide the 
steel fabricator in the assembly of angles, channels, and eye-beams 
into a riveted unit of steel, just the right span and supporting 
power for the place it is intended to fill; they may consist of 
the elevation and plans of a house, showing foundation, framing, 
outside and inside finish, electric wiring, water and gas piping — 
in fact every detail necessary to make the building complete. 

<H These specifications were originally made by draftsmen, skilled 
in the art of mechanical drawing. These men had first to lay 
the foundation for the more advanced work by learning the kind 
of equipment necessary for drawings of various kinds, the use 
of the T-square, the triangle, the ruling pen, and all the other 
instruments which must be used from time to time. They had 
to train their eyes to visualize objects and measure distances 
and their hands to draw with precision lines of uniform width 
and accurate direction. They had to learn the rules of geomet- 
rical construction; the methods of representing plans and eleva- 
tions of objects; and the principles of orthographic and isometric 
projection and profile work. 

<I It would be well if every workman were able to make good 
mechanical drawings, for with the ability to make them would 
come the ability to interpret them. But there are often many 
reasons why this is not possible, and it is with the idea of giving 
the requisite amount of drafting knowledge and practice in 
visualizing the finished product from plans, elevations, and sec- 
tions that this little volume has been prepared. With a careful 
study of the lessons herein .laid down will come the ability to 
"read" a blueprint like a book, to translate every shade of mean- 
ing intended by the designer, and thus to be able to carry out 
the job in an accurate, efficient, and workman-like manner. 



CONTENTS 



The page numbers of this volume will be found at the bottom of the pages; 
the numbers at the top refer only to the section. 



BLUEPRINT READING 

PAGE 

Introduction 11 

Process of making blueprints h 11 

What blueprints should show 12 

General directions 13 

Meaning of projection 15 

Lines 16 

Symbols used . 21 

Analysis of typical blueprints 24 

Saddle nut „ 24 

Back clutch pinion 26 

Down-feed worm wheel 28 

Intermediate shaft clutch . 30 

Details of four machine pieces 31 

Center rest top 33 

Center rest base 34 

Center rest assembly 35 

Work spindle slide 35 

Drawing-in bolt 36 

Knee shaft clutch 37 

Back tool post . 38 

Center arm head '. 39 

Brass globe valve , 40 

Assembled cone gears . . . . ; 41 

Face gear 42 

Down-feed worm 43 

Saddle adjusting lever 44 

Top pulley bracket 44 

Shaft-bearing pedestal 47 

End shield 47 

Armature head 48 

Details of typical armature punchings 49 

Details of typical field punchings 50 

Gears used on 12-inch merchant mill 51 

Bevel gears for rolls on sheet bar and slab-mill steam flying shear 

table •'.' 52 

Motor coupling for rod mill drive v 54 

Binder arm for rope take-up 55 

Parts of shuttle mechanism for loom 56 



CONTEXTS 

Analysis of typical blueprints (continued) page 

Details of geared mechanism used on Crompton-Knowles loom 57 

Miscellaneous mechanisms used on Crompton-Knowles looms 58 

Brass check valve 58 

Spindle 60 

Roof truss 61 

Plan of foundry building 63 

Fire insurance map 64 

MECHANICAL DRAWING 

Instruments and materials 67 

Drawing paper 67 

Pencils 69 

T-square 70 

Triangles 72 

Compasses 76 

Bow pen and bow pencil 79 

Drawing pen 79 

Ink 80 

Scales 81 

Protractor 81 

Irregular curve 82 

Beam compasses 82 

Lettering 83 

Forming 83 

Spacing 84 

Inking 84 

Style ' 85 

Instructions 88 

How to hold instruments 88 

Don'ts in drafting work ....*. 91 

Preliminary line problems 92 

Geometrical definitions 107 

Lines 107 

Angles 108 

Surfaces 108 

Polygons 108 

Triangles 109 

Quadrilaterals 1 10 

Circles Ill 

Measurement of angles 112 

Solids 113 

Polyhedrons 113 

Prisms 113 

Pyramids 114 

Cylinders 115 

Cones 115 

Spheres 116 



CONTENTS 

Geometrical definitions (continued) page 

Conic sections 117 

Ellipse 117 

Parabola 118 

Hyperbola 118 

Rectangular hyperbola 119 

Odontoidal curves 119 

Cycloidal curves 119 

Involute curves 120 

Geometrical problems 121 

Orthographic projection 139 

Definitions 139 

Comparison of third- and first-angle projection 141 

Projection methods 142 

Projection lines 146 

Ground line 146 

Rules of projection 147 

Practical problems 149 

True length of lines 153 

True length by revolving horizontal projection ' . 154 

True length by revolving vertical projection 154 

Representation of objects 155 

Rectangular prism of block 155 

Triangular block with square hole 156 

Rotating and inclining of objects 156 

Method of rotating object 156 

Pyramid 157 

Cylinder in inclined position to horizontal plane 158 

Intersections 164 

Planes with planes 164 

Planes with cones or cylinders 169 

Development of surfaces 172 

Right cylinder 173 

Right cone 174 

Cone 175 

Regular triangular pyramid 176 

Truncated circular cylinder 177 

Isometric projection 179 

Isometric of cube 179 

Applications of isometric projections 182 

Characteristics of various isometrics 182 

Oblique projection 189 

Comparison with isometric 189 

Characteristics of method 189 

Line shading 192 

Lettering 194 

Types of lettering 194 

Size of letters 194 

Titles for working drawings 199 



BLUEPRINT READING 



INTRODUCTION 

Definition of Blueprint. A blueprint as used by engineers and 
by workmen in the various industries is a reproduction of what is 
known as a working drawing. A working drawing, as made by the 
draftsman, shows by means of lines what the piece, machine, or 
construction is, gives the necessary working dimensions and what- 
ever other data the workman needs to know in order to build the 
piece or the structure; in other words, it is the drawing by which 
the workman does his work and to which he looks for his informa- 
tion when building the structure or machining the part. However, 
it is essential that the working drawing itself be preserved for 
reference in the drafting room, and therefore a blueprint is made 
from the working drawing and this is what the workman uses at 
his machine or in the field. The lines, numerals, and letters on 
the original working drawing are black on a white background but 
these appear on the blueprint as white lines on a blue background; 
hence the name blueprint. 

Process of Making Blueprints. Blueprints are contact prints; 
that is, the blueprint paper and the working drawing are in con- 
tact with each other while exposed to the light. Blueprint paper 
is a strong rather tough white paper coated with a solution which 
is sensitive to sunlight and turns blue when exposed to sunlight 
and then washed in clean water. Those firms which use large 
numbers of blueprints often coat their own paper. Most firms, 
however, buy it in the open market already coated with the 
prepared sensitive solution. In making a blueprint, the working 
drawing is laid face down on a sheet of clear glass and the blue- 
print paper, cut to a size slightly larger than that of the drawing, 
is laid on the drawing with the colored, or sensitive, side next to 
the drawing and by means of a clamping frame is brought and 
held firmly in close contact with the drawing. The holding frame 
is then tipped and held in a position to allow the sun or other 
strong light to shine squarely through the glass. The light thus 



2 BLUEPRINT READING 

passes through those parts of the drawing on which there is no ink 
and effects a chemical change in the light-sensitive blue coating. 
The light does not shine, or pass, through the inked lines of the 
drawing, the lettering, or the numerals. After a short exposure 
to a strong light the clamps are removed and the blueprint paper 
is taken out of the frame and thoroughly washed in clean water. 
The parts upon which the strong light shone turn a rich blue 
color; those parts which came under the inked lines were not 
affected by the light rays and wash up a clean sharp white. 

Importance of Blueprints. The blueprint from a properly 
made working drawing should contain all the information needed 
by the workman in his work and he should never ask for informa- 
tion until he is positive that it is not on his blueprint. It is well 
also for him to understand that his blueprint is an exact reproduc- 
tion of a drawing on file in the drafting room and that, if he implic- 
itly follows instructions and dimensions as given in his blueprint, he 
is protected in any argument which occurs over his work; in other 
words, if his work checks up with the blueprint he has worked 
from, any errors found in results are squarely up to the draftsman. 

What Blueprints Should Show. A blueprint is in a sense a 
picture of the piece, machine, or structure which is to be made or 
built. This picture is made up of views; for example, front view, 
top view, end view, etc. (See "Mechanical Drawing,'' Part III, 
pages 73-79.) These views are made up of lines which would 
show clearly to the eye if the part, machine, or structure were 
viewed from the several positions noted; for example, a front view 
consists of those lines which would be clearly seen if the observer 
were viewing the part or machine from the front. The blueprint 
should also contain all the essential dimensions and indicate clearly 
from what surfaces they are to be taken In most cases, this is 
done by using a distinct arrowhead with the point resting against 
the line which represents the surface or the outline from which the 
measurement starts or from such a working line extended; that is, 
the line which represents a surface edge is lengthened to make it 
convenient for placing the arrowhead. Another arrowhead is 
placed against the line representing the surface where the measure- 
ment stops, and the two arrowheads are connected by a line called 
a dimension line and the given dimension is placed either in this 



12 



2" ACROSS FLATS 



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Fe* 



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TWO STEEL 

Fig. 1. Detail Drawing of Link Stud 



BLUEPRINT READING 3 

line or directly over it. Fig. 1 shows this. The blueprint will 
probably also contain lettered directions; some surfaces are to be 
ground, and the word "grind" may be lettered on those surfaces, 
others are to be polished, and 
on those the word "polish" may 
be placed. 

Reading Blueprints. To be 
able to read a blueprint is as 
essential to a workman's success 
as to be able to read printed mat- 
ter. To read blueprints readily, 
he must know some of the prin- 
ciples of making drawings. These are explained to a considerable 
length and with close attention to detail in "Mechanical Drawing," 
Parts I, II, and III, and these books should be read most care- 
fully. This is somewhat equivalent to learning the alphabet in 
learning to read printed text. The workman should first under- 
stand that a blueprint is a record of instructions given him to 
read. Second, he should realize that the language used by the 
draftsman in making his drawing is largely a language of lines and 
that, unless he knows how to read lines, the instructions recorded 
on the blueprint are essentially in a foreign language. (Read care- 
fully and memorize page 41, "Mechanical Drawing," Part II.) 
To read a blueprint, the first thing is to study the several views 
until one has a good mental picture of what he is to construct. 
As the blueprint is a flat surface, it is necessary for the workman 
to use his imagination to make the lines and views lift up from 
the paper. When a clear-cut mental picture has been formed, the 
dimensions should be studied until understood. Next all the let- 
tered text should be read and considered. Carelessness in any 
one of these three respects is not to be excused. 

GENERAL DIRECTIONS FOR READING BLUEPRINTS 

Method of Obtaining Views. As already noted in the "Intro- 
duction," a blueprint represents the information which the drafts- 
man is seeking to convey to the workman. It becomes necessary 
then for the workman to think somewhat as the draftsman thinks. 
Plate I, page 14, consists of three separate outlines, or diagrams. 



13 



4 BLUEPRINT READING 

These diagrams are known as views and are obtained by project- 
ing the outlines of the piece point by point onto an assumed plane. 
(Read carefully the matter under "View" and "Projection" in 
"Mechanical Drawing," Part III, page 73, and study Fig. 95.) 
In the case in hand, the paper on which the drawing is made is 
the plane, and as the blueprint is an exact reproduction, line for 
line and point for point of the original, it also can be said to be 
the projecting plane. As an aid in understanding what the drafts- 
man did when he made these views and why they are placed on 
the paper as they are, let the reader imagine that with a sheet of 
paper he has made a box having all the corners and all the sides 
square with each other. Assume that the paper box is transparent 
as glass is transparent and that a piece of work might be hung 
inside the box centered with the sides and corners. Let us now in 
imagination hang various objects one at a time in this paper box 
centered squarely with its transparent sides through which they 
may readily be viewed. (Carefully study Fig. 102, ''Mechanical 
Drawing," Part III, page 79.) If the first object selected is a per- 
fect cube, for example, an ordinary playing dice, then, viewing this 
from every side of the box, it is at once evident that all the views 
are the same in outline. If the outline dice is drawn, with a pencil, 
on each side of the box, as seen through that side, we will have six 
outlines all of the same size and shape. If an ordinary playing 
domino is substituted for the dice, the views when looking into the 
top and the bottom of the box will be alike in outline. Those 
seen when looking into the right and the left ends will also be 
alike, as will the views seen when looking through the back and the 
front sides of the box. If the pencil is used as before, six outlines 
are shown, but instead of their being each like the other, there are 
three pairs of views, each pair distinctly different from the others. 
If these penciled views are labeled top, bottom, front, back, right 
end, and left end, and the paper box is cut along its corners and 
the paper then tacked flat on a board, we have a drawing of the 
piece giving six views labeled top, bottom, etc. 

Instead of doing all this box work, the draftsman first trains 
his hands as shown in "Mechanical Drawing," Part I, pages 22 29, 
to use in a neat and skillful manner the various tools shown and 
described in pages 1-17. He also trains his hands to produce and 



14 



BLUEPRINT READING 5 

his mind to remember the various outlines shown in "Mechanical 
Drawing," Part II, pages 41-54. In addition, he must learn to 
imagine what he is going to make a drawing of, or, as it is termed, 
see the thing in space, which means form a reasonably complete 
mind picture of the piece he is to draw. In "Mechanical Draw- 
ing," Part III, pages 80-86, it is shown by what methods the 
draftsman avoids having to use a box with transparent sides when 
making a drawing; by using the tools shown in Part I, pages 1-17, 
in a certain conventional manner, he gets all the views he wishes 
on a sheet of paper tacked flat on a board. 

Number of Views Needed. It will be recalled that in view- 
ing the domino centered in the box, while we had six separate 
views, certain views duplicated and three views were sufficient to 
show clearly the outline of the piece. When drawn, some machine 
parts need several different views; others need only a single view. 
In Plate I the draftsman considered that he could get all the infor- 
mation the job needed on three views, namely, a front view a 
top view, and an end view. 

Interrelation of Views. In reading Plate I and other blue- 
prints, it will be observed that the top view and the front view 
center, line for line and point for point, on the same vertical center 
line, also that the front view and the end view center, line for line 
and point for point, on the same horizontal center line. Plate I, 
"Mechanical Drawing," Part I, page 26, shows a series of horizon- 
tal lines and a series of vertical lines, and it is explained in Part 
III, pages 73-86, how the vertical and horizontal reference lines 
work out in the drafting room. In some of the plates, it has been 
found necessary to readjust the different views to accommodate them 
to the small size plate, in violation of the rules of third angle projec- 
tion. The student should make allowance for these discrepancies. 

Meaning of Projection. To understand thoroughly what the 
term "projection" means, it is well to study the action of light as 
we view an object. Take as an example a man walking along the 
street. Our view of that man is made possible by the fact that 
light is reflected from his body into our eyes. This is true of all 
objects which we view with our eyes and we say that we see the 
man or the object. In other words, the light which is reflected, 
or thrown back, from the man or from the object into our eyes 



15 



6 BLUEPRINT READING 

gives us a view of the man or the object. If the man or the object 
faces toward us, we get a front view, if away from us, a rear view. 
"While the object itself is not a source of light, it is so treated in 
viewing it and the light is said to be projected from the object viewed. 
When a view drawing is made, it is often known as a projection. 

Projection of House. In "Mechanical Drawing," Part III, 
page 118, Fig. 160, is shown an isometric projection of the ordinary 
house. As an example of ordinary projection, suppose we select 
such a house and view it from its several sides, at a distance of 
not less than 100 feet from the several sides. Taking the front 
end first, the viewer will note that it appears as a flat wall having 
a rectangular outline with its top line in the shape of an inverted 
V. A side view gives a bottom line where the house rests on the 
foundation, two vertical, or upright, lines at each end of the side, 
a horizontal, or level, line to show the eaves, and a second hori- 
zontal line above this to represent the ridgepole. If these two 
views have been penciled out on a sheet of paper to some exact 
size, they will show what the outline of the house is. We can also 
show on these views the several doors, windows, etc., as we see 
them when viewing the front end and when viewing one side of 
the house, and if the rear end and the opposite side have the same 
doors, windows, etc., in exactly the same positions, the workman 
would be able from these two views to construct walls which 
would be as desired. If, however, the rear end had the doors or 
the windows placed differently from those on the front end or if 
they were not of the same size even though placed in the same 
manner, the workman would need a rear view to show him this 
fact. The same thing would hold true in respect to the sides of 
the house. Also, if the roof itself were broken up by windows, a 
top view showing their size and layout would be necessary for the 
workman. For convenience in making and reading the drawing, 
the several views are universally arranged for shop use exactly 
opposite the surfaces which they represent, as noted in the use of 
the box with transparent sides. 

Lines. Working Lines. A study of the views in the several 
blueprints in this book shows at once that each view is made up 
of straight hues and curved lines. The straight lines, or right 
lines (as they are often termed by draftsmen), are used to repre- 



16 



BLUEPRINT READING 7 

sent the edges of plane surfaces. How such lines are drawn and 
the tools used for drawing them are shown in "Mechanical Draw- 
ing/' Part I, pages 22-25. In the example just used, two upright 
straight lines a certain distance apart would be used to show the 
corners of the house. A circle line may show the edges of a 
cylinder or a hole in any surface, for example, a bolt hole or, in a 
house, a circular window. By using a combination of straight 
lines and part of a circle, the rounded end of a straight-sided 
bolt, for example, can be shown. Where the edges are neither 
straight lines nor parts of a circle, they are drawn with a special 
tool having an irregularly curved edge, which can be fitted to the 
desired line shape. (See Figs. 32 and 33, "Mechanical Drawing," 
Part I, pages 16 and 17.) A view, then, may consist entirely of 
straight lines, entirely of curved lines or of circles, or of a com- 
bination of all these. It must in any case be clearly noted that 
any working line, straight or curved, is used to show where a sur- 
face on the work changes its direction, in other words, to show the 
edge of a surface. If the object viewed is a solid piece, for example, 
a bolt, all the working lines in the several views are solid and con- 
tinuous straight or curved lines. If the work has holes through it 
or has hollow places hidden inside it, the lines which show the 
hidden edges are drawn as dots and the line is termed a dotted 
line. (See Fig. 110, "Mechanical Drawing," Part III, page 84.) 
In studying a blueprint then, it will be understood that the dotted 
lines in a view represent surfaces and edges which are hidden from 
the viewer's sight when the object is viewed from the side shown. 
In the case, of the bolt, Fig. 1, a view of the head end would 
show the body of the bolt as a dotted circle. In a blueprint of 
the house, the wall timbers, partitions, etc., which are not seen 
from the outside, would be shown as dotted lines. 

Dimension Lines. While the house outlines as they now stand 
give a general idea of how its exterior would look, they do not 
show its size or the sizes of the several doors, windows, trim, etc. 
To give this information, use is made of dimension lines drawn 
between points on the lines which make up the several views. 
To indicate the place where the measurement is to start and the 
point where it must stop, each end of a dimension line has a neat 
arrowhead, the point of which just touches the line at which the 



17 



8 BLUEPRINT RFADIXG 

measurement starts or stops. Somewhere in the length of a 
dimension line are placed the numerals which give the exact 
measurement of the work as indicated by the arrow points. 
Dimension lines usually show on the blueprint much thinner than 
the lines which make up the views. This fact and the fact that at 
their ends are prominently placed neat arrowheads render it easy 
to avoid confusing them with the working lines of the blueprint. 

In case a dimension line cannot readily be placed on the view, 
the working lines may be lengthened, or extended, a short distance 
from the view and the dimension line can then be drawn between 
the extended lines with the points of the arrowheads resting exactly 
against the extended lines. The end of an extension line, as it is 
called, should never quite touch the working line which it extends. 

Section Lines. In addition to the working lines and the 
dimension lines on the blueprint views, the workman will, in some 
cases, find a series of parallel lines drawn closely together at an 
angle to the working lines of the view. These are known as section 
lines and are used by the draftsman to tell the workman that 
the part of the view covered by such lines is as if the work had 
been cut through and a portion removed. (Plate I, Fig. 3, 
"Mechanical Drawing, 3 ' Part I, page 26, shows an example of 
section lines.) Sections open up the interior of an object or a com- 
bination of working parts, for example, the headstock of a lathe, 
and give a clear view of the inside. To use a homely illustration, 
the draftsman seeks the same effect as the grocer does when he 
cuts a melon in halves for the customer's inspection. A view so 
drawn is said to be sectioned; hence the term section lines. In the 
case of the lathe headstock, some of its parts may be of cast iron, 
some of bronze, some of steel, etc. To show which parts are of 
cast iron, of steel, or of bronze, the draftsman makes use of 
various arrangements of section lines, each arrangement showing 
a different material. In Plate III, "Mechanical Drawing," Part I, 
page 35, are shown and named the common arrangements of lines 
to -how sections of different materials, viz, metals, wood, brick, con- 
crete, etc. The workman should study those common to his work. 

Drawing Sheet Sizes. In "Mechanical Drawing," Part I, 
page 2, is given a list of sizes of drawing sheets. While different 
shops may use different sizes for their blueprints, a- a rule each 



18 



BLUEPRINT READING 9 

shop has some regular system of sizes. A common system for 
machine shops makes the largest regular sheet 24"X36" and lists 
it size A. Such a sheet will fold and cut to give two B sheets 
18"X24". Continuing the folding and cutting gives a C size 
12"Xl8"; a D size 9 ,/ Xl2 ,/ ; and an E size 6 ,, X9 // . A machine 
shop blueprint is usually trimmed to one of these sizes. 

Methods of Showing Large Work. Reducing Scale of Drawing. 
Several methods are used to make it possible to show a view of 
large work on a small sheet of paper. The view is often made a 
reduced size, which is usually spoken of as making it to a reduced 
scale. The term "scale" in such a case means that the length of 
the working lines in the blueprint views has a definite proportion 
to that of the actual lines of the work itself; for example, if the 
circles which represented the rim of a 24-inch pulley were drawn 
in a view as 12-inch circles, the view would be one-half size, or 
to one-half scale. If the circles were made 6 inches in diameter, 
the view would be to one-quarter scale. While in these cases the 
dimension lines would be, respectively, 12 inches or 6 inches in 
length from arrow point to arrow point, the dimension figures 
would read the exact size, 24 inches. For the reason that a blue- 
print view on a reduced scale does not give the average workman 
a good size picture of the work, it is customary to have the views 
show the work to exact, or full, size whenever it is practicable to 
do so. Such a view is known as a full-size view, or a full-scale 
view. The common machine shop view scales are one-eighth, one- 
quarter, one-half, three-quarters, and full size. Another way of 
expressing view scales is in inches to the foot; for example, a one-half 
scale is 6 inches to 1 foot and a full scale is 12 inches to 1 foot. 

Showing Parts of Work. Another way of getting a view of a 
comparatively large piece of work into a small space on a blue- 
print is to show only a part of the work in the view. In the case 
of the pulley just mentioned, if the blueprint view showed one- 
quarter or one-half of the entire pulley, the average workman 
would be able to get all the directions necessary from the view to 
complete the work. 

Breaking the Piece. Yet another way by which the space 
utilized to represent a piece of work in blueprint views can be les- 
sened is what is known as breaking the piece. To illustrate, use is 



19 



10 BLUEPRINT READING 

made of the front view of a long bolt or shaft of relatively small 
diameter. If such a piece were shown full scale, its working 
length lines might reach the entire length of the blueprint or even 
farther. If the body of the bolt or shaft is of uniform size and 
shape, it is sufficient to show a portion of the body near the head 
and a portion near the threaded, or opposite, end, and the portions 
shown may be brought close up to each other and thus little space 
used for the view. When analyzing the several blueprints repro- 
duced in the following pages, the ways in which space is utilized 
in representing the parts of the work will be noted. 

Shade Lines. It must be admitted that the average blue- 
print view of a piece of work is a rather flat and dead thing and 
that some imagination on the part of the workman is needed to 
give it life and to make it lift up from the paper and really have 
form and substance. Fortunately for the machine shop workman 
who is just learning to read blueprints, much of his work comes to 
him roughly in the form in which he is to finish it. This is espe- 
cially so when he is finishing ordinary castings. There are several 
methods used at times to give the blueprint views more "life". One 
much used method is to make certain of the working lines of 
increased thickness to represent a shaded portion. These heavier- 
working lines are known as shade lines and aid somewhat in mak- 
ing the view stand, or lift, up from the paper. Such shade lines 
are used to a lesser extent now than formerly, as the workman is 
supposed to use his imagination when reading blueprint views. 

Line Shading. The term shade lines should never be confused 
with the term line shading which refers to a decidedly different use 
of lines. Line shading as commonly used consists of a series of 
lines placed on the view within its working lines and arranged in 
such a manner as to give a picture effect to the view. In "Mechan- 
ical Drawing," Part III, pages 126 and 127, are shown a variety 
of objects which have been line shaded. Comparison of these 
illustrations with Figs. 78, 81, and 84, "Mechanical Drawing," 
Part II, pages 49 and 50, clearly shows what line shading does to 
liven up a view. As is the case with shade lines, line shading is 
used less in machine shop drawings than it formerly was. 

Finish Lines. Another line used in blueprint views is some- 
times termed a finish line. Such a line is usually broken up into 



20 



BLUEPRINT READING 



11 



dashes and dots and is then known as a dashed line. It is placed 
on the view close to a working line to indicate that the surface 
represented by the working line is to be finished. Dashed lines 
are now little used for this purpose because of the chance of their 
being confused with dotted lines used to represent hidden surfaces 
and edges, and other methods of indicating finished surfaces are 
popular. Brown & Sharpe practice is to use a red pencil to draw 
a full red line on the blueprint views close beside all working lines 
which represent finished surfaces. A common method of indicat- 
ing finish is to place a letter / across all working lines which 
represent finished surfaces. 

Symbols Used. There are a number of words which often 
appear on blueprint views, each conveying certain information, and 
the workman must be familiar with the more commonly used ones 
to read his blueprint readily. The word "ream" near a hole 
shown in the view means that the hole is to be finished by ream- 
ing it; the word "tap", if so placed, indicates that the hole is to 
be tapped. The terms which the workman is most likely to find 
on his blueprint views are ream, tap, grind, polish, scrape, frost, 
taper, crown, and drill. He will also often note the letters F.A.O. 
near certain views; when so found, they denote that the piece of 
work is to be finished all over and the letter / is left off the work- 
ing lines. It is also common machine shop practice to place on 
the blueprint the name of the piece of work, the number wanted, 
and the material to be used, all neatly lettered. The several 
materials used in the construction of machinery are usually indi- 
cated by their initials, for example, M.S. for machinery steel. To 
read blueprints easily and accurately, the workman should learn 
the symbols used, the more common of which are given and 
defined in the following tabulation: 



F A.O finished all over 

f finished surface 

RAD radius 

DIAM diameter 

R.H right hand 

L.H left hand 

P.R piston rod 

P. Tap pipe tap 

CTRS centers 



C.I cast iron 

S.C steel casting 

Bz bronze 

C.R.S cold rolled steel 

T.S tool steel 

O.H.S open-hearth steel 

W.I wrought iron • 

M.S machinery steel 



21 



12 BLUEPRINT READING 

Special notes neatly lettered are often placed on the blueprint and 
these notes should always be read carefully. In "Mechanical 
Drawing," Part I, pages 17-21, and Part III, pages 128-134, are 
shown examples of lettering. Each and every dimension line 
should have in clear distinct figures, either on the line or in a 
break in the line, the exact dimension which the dimension line 
represents. Dimension figures should be clear, distinct, and easily 
found and read. (Study Plate I, Fig. 4, "Mechanical Drawing," 
Part I, page 26.) Certain working variations in dimensions are 
allowable in all work. These are termed tolerances and should be 
given on the blueprint. They are usually preceded by the sign =*= 
and are placed near or follow the given dimension. If the toler- 
ances are not to be found, the workman must learn what the 
practice of the shop is in regard to this point. 

Conventions Used. Certain conventions, as they are called, 
are often to be found on blueprints. Take screw threads as an 
example; they are seldom shown on a blueprint as actual threads 
but are indicated by an arrangment of parallel lines across the sur- 
face meant to be threaded, Fig. 1, page 3, and a note is usually 
lettered on or near the threaded surface giving the number of 
threads per inch and the form of the threads. Gear teeth are 
seldom shown on a blueprint; a lettered note is used instead to 
state the number of teeth in the gear and whether they are 
involute, cycloidal, or otherwise. 

Intersections and Irregular Surfaces. While, in most cases, 
the workman can get the needed information from a sufficient 
number of views of the ordinary method of projection, this is not 
always true where two surfaces meet at an angle, especially if 
they meet or intersect at other than a right angle. As an example 
of such a case, take the spout of an ordinary tin coffee pot where 
it joins the body of the pot. In uniting the two, it is necessary to 
know just what the shape of the hole should be and its size; also, 
in making up the pot body and the spout body, each of which is 
usually tapered, it is necessary to know the exact shapes and sizes 
to which the sheet tin must be cut. All sheet-metal work is full 
of such problems, as well as work in leather, for example, shoe 
tops, bags, etc. To obtain the desired forms of the holes and the 
body of a sheet-metal object, it is in effect cut open and flattened 



22 



BLUEPRINT READING 13 

out as if it were a sheet of paper. The methods by which such 
problems are solved are very clearly shown in "Mechanical Draw- 
ing/' Part III, under the headings "Intersections," pages 98-106, 
and "Development of Surfaces," pages 106-113. While the work- 
man's blueprint should show the already developed surface, or pat- 
tern, he will better understand his job if he knows how such a 
pattern is made. 

Single Picture Views. The practice in some shops is to fur- 
nish the workman with a small blueprint which has a single view 
of the piece he is to work on. These sketches can be made by 
the use of the regular draftsman's tools or, given sufficient artist's 
skill, may be made free hand. The excellent examples of such 
sketches given in Plates XXIX, XXX, and XXXI were, in the 
original, entirely free hand. Where one view is sufficient to show an 
object in its true shape, it must show the object tipped and turned 
into such a position as to give a picture view. The sketch artist 
views the object from a variety of angles, finally decides which view 
best shows the piece, and makes that the blueprint view for the 
workman. In "Mechanical Drawing," Part III, pages 113-125, 
the methods used to obtain these single picture views are described 
and illustrated. 

Importance of Careful Study. The careful reader of the pre- 
ceding text must now be impressed with the need of knowing 
things. The way to know a thing is to study it, just as a child 
studies his book when learning to read. The child first learns the 
simpler words, how they look, what letters of the alphabet are 
used in spelling them, how the words are pronounced, etc. Any- 
one who is willing to study this text and "Mechanical Drawing," 
Parts I, II, and III can learn how to read ordinary blueprints 
readily. To assist the reader of this text in doing this, a variety 
of simple blueprints have been selected for analysis. Although 
they by no means cover all classes of work, nevertheless, they have 
been selected from a large number as being the more typical 
of their kind. Carefully study each blueprint as well as the text, 
for, in the first place, you will become acquainted with good 
practice as carried out by several well-known firms and, in the 
second place, you will, by this thorough analysis, train yourself to 
see in any blueprint everything that was intended to be brought out. 



23 



14 BLUEPRINT READING 

ANALYSIS OF TYPICAL BLUEPRINTS 

PLATE I 

SADDLE NUT 

It is evident that Plate I shows three views of a saddle nut. 
Before starting to read the views, the workman should read 
the lettered data at the top of the blueprint. From this he gets 
the name of the piece he is to make, "saddle nut," the number 
required, "one, on a single machine," the name of the machine to 
which the piece belongs, "5-foot boring mill," and the piece num- 
ber, "14049." He next reads the lettered data at the lower edge 
of the blueprint and learns what material he has to work on, in 
this case, bronze. If this plan has been followed out, the workman 
now knows that he is to make a certain number of bronze saddle 
nuts, each of which is a part of a 5-foot boring mill. 

The several views are a front view, a right end view, and a 
bottom view. The front view shows the piece as it would look when 
set on its flat base on the bench, with its long side toward the 
viewer. The right end view shows the piece as it would appear 
if set on the bench as before, but so placed that the right end 
would face the viewer as he stood at the bench. The remaining 
view shows the bottom, or base, of the piece as it would appear 
if the workman picked the piece up from its first position on the 
bench, held it above his head, and looked up at its bottom side. 
As both ends of the saddle nut are alike, no left end view is nec- 
essary; and as nothing is to be done to its upper, or top, surface 
or to its rear side, neither a top nor a rear view is necessary. 

The dotted lines through the front and the bottom views 
show that there is a hole through the length of the work and the 
right end view shows that the hole is circular in shape. As the 
dotted lines through the front and the bottom are double lines 
exactly centered with the center lines of these two views and as 
the right end view shows a full-line circle and a dotted-line circle, 
something more than these lines are needed to tell us just what 
this hole is. Between the front view and the right end view are 
certain notes nicely lettered. They state that the hole has a left- 
hand square thread, four threads to the inch through its length, 



24 




15 

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14 



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BLUEPRINT READING 15 

make everything clear as to what the hole is, and explain the name 
"nut" given to the piece in the title. 

Near the base of the front and the right end views are cer- 
tain other dotted lines which, of course, represent hidden surfaces 
or holes. When we look at the bottom view, it is easily seen that 
these are round holes. By reading the notes placed at the right 
of this view and by following the arrows, we learn that two of 
these holes are to be made to fit a No. 5 taper pin and that the 
two larger ones are to be drilled and tapped for a f-inch screw. 
This view also shows that there is a screw hole and a pin hole in 
each end of the piece and that the screw and the pin holes are 
placed in corners diagonally across from each other. It can also 
be seen by reference to the several views that the screw holes and 
the pin holes are placed on the same center lines. If the workman 
is used to general machine construction, he will know that the 
screw holes are for the bolts which are to hold the saddle nUt to 
the saddle and that the pin holes are for the taper pins which 
locate and hold the nut to an exact position. The bottom view 
shows by dimension lines placed just above the view that the 
holes are to be placed 3 inches from each other along the length 
of the piece and f inch in from the edges of the base. The end 
view shows by dimension lines placed just below the view that 
along the width of the piece the holes are 2 inches apart and 
| inch in from the sides. The workman should understand that 
when the dimension lines are shown in this manner, the center-to- 
center distance is the more important one. In this case, the 2-inch 
and the 3-inch dimensions are of more importance that the f-inch 
dimensions, these latter being probably given to inform the work- 
man that the holes must be symmetrical with the base of the nut. 

Attention is called to the placing of the dimension lines 
between or at the side of the views and to the fact that the arrow 
points touch extension lines drawn to nearly touch the surface 
lines. Dimension lines placed between the front view and the 
bottom view show that the saddle nut is 4f inches long over all 
and that the over-all length of the base is 4 \ inches. Dimen- 
sion lines placed just below the right end view show that the 
base of the nut is 3 \ inches wide over all. A dimension line 
placed just above the end view shows that the rounded part of the 



25 



16 BLUEPRINT READING 

nut is 3 inches. While reading the over-all dimensions, for example, 
the 4f-inch, the 3J-inch, and the 3-inch dimensions, the workman 
should at the same time see whether or not his castings measure 
up fairly close to these dimensions with finish allowances. 

Attention is called to the fact that all the dimensions are given 
either in whole numbers or in whole numbers and common frac- 
tions, with the exception of the dimension for the bore of the hole, 
which has added to it the decimal 0.003. This would indicate that 
the various dimensions given, with this one exception, are not of 
exceptional importance, or that the workman will be furnished 
with a special gage, or that the work will be jigged. 

In this blueprint, it will be noted that the surfaces to be 
finished are indicated by the letter / placed on the working surface 
lines. As thus indicated, the base of the nut, the right-hand end, 
and the hole through the nut are to be finished. 

PLATE II 
BACK CLUTCH PINION 

The lettered data at the upper edge of Plate II informs us 
that the piece is a back clutch pinion for a 5-foot boring mill and 
that one is required on each boring mill. Lettered data also tells 
us that the material is machinery steel and that the rough stock is 
5| inches in diameter and 4| inches long. 

The views given are a front view and a left end view. As 
the work is round with a plain squared-up right end, two views, 
as shown, are sufficient for the workman to understand what the 
piece is as well as to get all his dimensions. As an aid in read- 
ing the blueprint, the front view shows the piece as if it had 
been cut in halves through its length. The parts of this view 
which show where the cutting is made in solid stock are cross- 
lined at an angle of 45 degrees with the working lines. Referring 
to "Mechanical Drawing," Part I, page 35, it is scon that the 
cross-section lines are arranged to show that, as previously stated, 
the material is machinery steel. 

A- the first machine operation on this piece of work is that of 
getting a hole chucked through its axis, or length, the workman 
will naturally read his drawing for the size of the hole. At the 
right hand of the front view we find a dimension line with the 



26 



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27 



BLUEPRINT READING 17 

arrow points touching the diameter lines of the hole extended, as 
explained in "General Directions for Reading Blueprints." The 
figures placed in the dimension line inform us that the hole is to 
be made 2| inches, and as the left end view shows a central circle, 
the hole is a round one. The word "ream" placed on the dimen- 
sion line to the right of the dimension figures shows that the hole 
is to be drilled sufficiently small to permit it being reamed to its 
exact figured size. This dimension, as well as all the other dimen- 
sions, in the original blueprint, read two times the actual distance 
between the arrow points as shown on the views. The views in 
the original blueprint are then one-half the size of the actual 
piece of work and are drawn to one-half scale, in other words, 6 
inches on a view represents 12 inches on the actual work. 

The next two machine operations on this piece are to square 
the ends to the over-all length and to turn and finish it to the 
exact diameter. By following the end extension lines upward, we 
find at their upper ends a single dimension line having arrowheads 
with their points touching the extension lines. By reading the 
numeral placed in the line, it is found that the over-all length is 
4 inches. Thus far this blueprint is very easily read. 

Before starting work on the diameter, the views and the let- 
tered text must be more carefully read. The name of the piece, 
"back clutch pinion," and a study of the views show it to be a 
gear with a clutch on its left-hand end. 

Following out the extension lines to the left and to the right 
of the front view, which represent the several working diameters, 
we learn that the surface where the gear teeth of the pinion are to 
be cut is 5 inches in diameter. By following the upward extension 
lines, it is seen that the right-hand ends of the teeth do not start 
at the exact end of the stock but \ inch to the left of this. The 
extension lines also show by proper dimension lines that the faces 
of the teeth are to be 2\ inches long. In this same view, the 
upward extension lines and dimension lines show that the remain- 
ing length of the piece from the left-hand end of the pinion teeth 
is 1J inches. Following the diameter extension lines to the left, 
we learn that the diameter of this part of the work is 4| inches. 

A further study of the left end of the front view and of the left 
end view will show that the inner diameters of the clutch teeth are 



27 



18 BLUEPRINT READING 

counterbored out to 3J inches with a depth of J inch. The right- 
hand end of the work is turned into the form of a hub having, 
according to the dimension line near that end, a small diameter 
of 3 J inches but curving up into a fillet. Both views show that 
there is a tapped hole through one side of the piece, and the let- 
tered data placed just below the front view tells us that the hole 
is to be drilled with a j^-inch drill and tapped with a f-inch tap. 
Both views show the clutch teeth. 

In the left end of the front view, extension lines carried 
upward have dimension arrowheads and numerals which show that 
the clutch teeth are to be cut \ inch deep. The left end view 
shows the general form of the clutch teeth. A lettered note just 
below this view states that there are to be five teeth and that the 
spaces between the teeth are to be \ inch wider than the teeth 
themselves. This indicates that the teeth in the mating part of 
the clutch and the teeth in the piece shown in this blueprint will, 
when in mesh, clear each other by a distance of \ inch. A let- 
tered note placed just below the front view informs us that the 
gear teeth are twenty-three in number and that a five-pitch cutter 
is to be used in cutting them. 

No finish / marks are placed on the various working lines 
in either view, but a lettered note F.A.O. tells us that the piece is 
to be finished all over. Two dotted lines on the front view indi- 
cate that there are hidden surfaces — in this case, the right-hand 
and the left-hand ends of the gear teeth of the pinion. If this 
text has been carefully studied, the reader will readily understand 
that Plate II really represents two pieces of work made solid 
in one piece of stock, namely, a toothed clutch and a pinion gear. 

PLATE III 
DOWN=FEED WORM WHEEL 

In reading Plates I and II, it will have been noted that in 
Plate I three views were needed to show the workman all he 
needed, while in Plate II two views were sufficient. In Plate III 
a single view shows all that is needed to build this piece of work 
completely. The data on the upper edge of the blueprint states 
that the piece represented is a down-feed worm wheel for the right- 
hand head of a 5-foot boring mill and that one is required. The 



& 



BLUEPRINT READING 19 

data on the lower edge tells us that the material is bronze, which 
is also indicated by the arrangement of lines in the cross-sectioning 
of the view. 

A worm wheel is a toothed gear with the gear teeth cut at an 
angle with the sides of its rim. This angle is such as will make its 
teeth readily mesh, or fit, into the screw threads of the worm 
which is used to drive it. While the driving worm is not shown 
on this blueprint, a dimension line at the right of the view, with 
one of its arrow points touching the center line of the worm wheel 
and the other touching another center line drawn near the lower 
edge of the blueprint, shows that the center-to-center distance of 
the worm and the worm wheel is 3f inches. Lettered data near 
the lower center lines states that the worm wheel is to have thirty- 
two teeth of |-inch circular pitch and that the worm will have a 
left-hand thread, two threads to the inch. 

In reading Plate III, let us first study the view itself. We 
will see that it is the view seen by a viewer facing the central axis 
of the piece and is, therefore, a front view. Lines drawn on the 
view at an angle with the working lines show that it is a sectional 
view, the piece having been cut along the center of its length pre- 
cisely as a watermelon is sliced along the center of its length. 
Since the view is shown in this way, it is somewhat easier to read. 
The fact that one view only is given to work from indicates : (a) that 
if the work were viewed from its ends, the views would show on 
the blueprint as circles; and (b) that the ends of the work are 
plain and squared up — hub and rim. The lettered data, as already 
noted, states that the piece is a toothed gear wheel. Altogether, 
the piece is shown to consist of a hub, a rim, and a connecting web. 

Following the upward extension lines and the dimension lines 
which they carry, it is seen that the over-all length of the piece 
is 2f inches and that the rim width is If inches. The upward 
extension lines and their dimension lines also show that the worm 
wheel hub extends, or projects, to the left of the rim a distance 
of | inch. Dimension lines on the body of the view show: (a) that 
the wheel hub is lyf inches long; (b) that the rim overhangs 
the right end of the hub yg inch; (c) that the right end of the 
hub projects J inch beyond the web; and (d) that the web is 
| inch thick. Following the extension lines to the left of the view, 



29 



20 BLUEPRINT READING 

we learn that the hub is 3 inches in diameter and that the chucked 
hole in the hub must ream If inches. These extension lines also 
show that the over-all diameter of the toothed rim is 5| inches. 

The curved diameter on the rim, as shown, is known as the 
throat diameter, to distinguish it from the over-all diameter. 
Following the extension lines to the left of the view, it is seen that 
the throat diameter is 5.4114 inches. The dimension line placed just 
over the rim with its arrow point touching the throat curve is 
drawn from the point where the short center line crosses the 
center line of the wheel rim. This dimension line indicates that the 
workman should machine the curved part, or throat, of the rim 
with a cutting tool having its cutting end formed to an arc of a 
circle of 1.0443 inches radius. The remaining radius dimension 
line has its arrow point resting on the curved working line which 
represents the inner surface of the wheel rim. 

The teeth in worm wheel rims are invariably cut or machined 
by the use of a special tool known in shops as a hob, or a hobbing 
cutter. In using a hob to cut the gear teeth, the workman has to 
know to what depth the cutting teeth are to be sunk into the rim 
of the wheel. The sketch in the upper right-hand corner of Plate 
III indicates in outline the teeth, or threads, on the worm and on 
the hobbing cutter. This sketch shows: (a) the angle of the sides 
of the threads; (b) the center-to-center distance, § inch; (c) the 
total depth of the hob thread, 0.3433 inch; and (d) the narrowest 
width of the hob thread and the space, 0.155 inch. The short 
note at the right of the view tells us that a keyway is to be cut 
in the surface of the hub hole | inch wide and Ye mcn deep. 

The/ marks placed on the working lines of the view show that 
the sides and the outer surface of the rim and both ends and the 
hole through the hub are to be finished. 

PLATE IV 

INTERMEDIATE SHAFT CLUTCH 

The piece shown in Plate IV is very nearly the same as that 
shown in Plate III. The practice is, however, that of another firm 
and the piece is represented by three views: a front view, a right end 
view, and a left end view. Reading the lettered data shows the 
piece to be an intermediate shaft clutch. The cross-section front 



30 



II 



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APPROVED 
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BLUEPRINT READING 21 

view shows that the material is steel, and a further reading of the 
lettered note tells us that the company knows this steel as Car- 
penter No. 5-317 steel. The left end view shows the general form 
of the clutch teeth. A line drawn across this view near a single 
tooth shows that a section has been sliced off at this point. The 
line is lettered A-B at its opposite ends to enable the workman to 
find the view of the part sliced off. 

Directly above the left end view is a small view named "sec- 
tion A-B". This shows a single clutch tooth viewed as if looked at 
from the inner, or small, end of the tooth. Extension lines pro- 
jecting upward from the working lines of the tooth show that the 
tooth sides incline 5 degrees from the vertical. No other view 
shown tells us this, and therefore it is necessary for the workman 
to have this small section. 

The right end view shows that the clutch teeth are slanted 
along their sides at an angle of 20 degrees, or, expressed another 
way, the sides of the clutch teeth make an angle of 20 degrees 
with each other. From a further study of this view, we learn that 
the inner surfaces of two adjacent teeth make an angle of 52 
degrees. The lettered note at the right and the arrowhead tell us 
that the inner ends of the clutch teeth are counterbored ff inch 
in diameter and \ inch deep. Just above the front view at each 
end arrow points have the numerals 0.124-0.126. The decimal 
fraction for § inch is 0.125; the numerals 0.124-0.126 then show 
that the J-inch depth must be cut to a tolerance of not more than 
0.001 inch above or below the figured depth, \ inch. The right 
end view clearly shows that this shaft clutch has gear teeth in its 
outer surface, and data under the front View states that there are 
to be fifteen teeth, ten pitch. The only other note for the work- 
man's use is that giving the size of the keyway. 

PLATE V 
DETAILS OF FOUR MACHINE PIECES 
General Data. In the study of Plate V and of all succeeding 
rlates, it will be assumed that the workman has thoroughly 
:• tudied all that has gone before and understands what is meant by 
'front, top, bottom, and end views, by sections, and by extension 
and dimension lines, and that he can find and read the dimensions. 



31 



22 BLUEPRINT READING 

Plate V is made up of four blueprints of small details and 
illustrates the way in which the Taft-Pierce Company send such 
into their shops. The number placed in the circle located in the 
upper right-hand corner of each small print is the part number of 
the piece and will be referred to in this text as the blueprint num- 
ber. It will be noted that blueprints Nos. 63, 440, and 113 are all 
blueprints of bolts. 

Swivel Table Stud. The piece shown in blueprint Xo. 63 is a 
swivel table stud for a semiuniversal grinding machine. A note 
placed just beneath the view states that the material is cold rolled 
steel, cyanide hardened. Only one view, a front view, is given, 
which indicates that the end views would show as circles. From 
this single view the workman can get all length dimensions and all 
diameter dimensions. Among the things to be noted in this blue- 
print are that the right end of the stud is to be threaded ten 
threads per inch and that some of the dimensions are given in 
pairs, for example, those of the body of the stud. This means 
that the length of the body and the diameter of the body, respec- 
tively, must lie within the given pair of figures for that dimension. 
Take the case of the body diameter; it must not be greater than 
0.999 inch nor smaller than 0.998 inch, a tolerance of one-half of 
one-thousandth inch above or below a central dimension. 

Wheel Guard T Bolt, Blueprint Xo. 440 is ' a wheel guard 
T bolt, and the note tells us that two are required and that the 
material is cold rolled steel. A front and a right end view are 
given. If a single front view of this piece were shown, the work- 
man would infer that the bolt head was a circle; the end view 
shows that the bolt head is square. A left end view instead of a 
right end view would indicate this equally well, but in that case 
the circles which represent the body of the bolt would be dotted 
circles instead of showing as they do in the right end view. There 
are no finish / marks in either view because the piece, as noted, is 
made from cold rolled steel bar stock, which has a finished sur- 
face, and when the bolt is turned to size, the outer surfaces of the 
head have the original finish of the bar. Moreover, to construct 
the rest of the bolt naturally finishes those parts. 

Diamond Tool Post T Bolt. Blueprint Xo. 113 is a diamond 
tool post T holt, and the lettered note states that one is required 



32 



23 

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32 



BLUEPRINT READING 23 

and that the material is cold rolled steel, cyanide treated. Two 
views of this piece are necessary. The views differ from those 
shown in blueprint No. 440, since the view showing the bolt head 
is a left end view. Placed in this way, the circles which represent 
the body part of the bolt show as dotted circles. Another inter- 
esting thing is that the body dimension of the bolt is given by the 
dimension figures as f inch, while a lettered note with an arrow- 
head tells us that the body of the bolt is turned to a diameter of 
ff inch and that the threaded part is f inch in diameter and has 
eleven threads per inch. The end view shows that the bolt head 
inclines at an angle of 60 degrees with the base line. 

Cross=Feed Connecting Link. Blueprint No. 345 shows a 
front view and a top view of a cross-feed connecting link. One 
only is required and both the lettered note and the arrangement of 
cross-section lines inform us that the material is cast iron. Where 
the shape of the cross-section is simple, as shown, it is usual to 
place it directly on one of the views rather than make an additional 
view. The cross-sections of pulley arms, connecting rods, and 
links are generally shown by this method. The workman in read- 
ing this blueprint should note that the reamed holes have limiting 
dimensions given and also that the thickness of the hubs is held to 
a small tolerance. The finish / marks clearly show what surfaces 
are to be machined. 

PLATE VI 
CENTER REST TOP 

The lettered data states that Plate VI is a blueprint of a 
center rest top. One is required and the material is cast iron. A 
short study will show the machinist that many of the dimensions 
are given to or from horizontal or vertical center lines; also that 
some of the dimensions are plain distances, in which case the 
dimension line has an arrow point at each end, while others are 
from a center point and give the radius from that point of the 
working line which represents the surface. When a radius dimen- 
sion is given, it is usual to place the initial letter R. or the letters 
Rad. after the dimension figures. 

In the front view, the workman should especially note that 
the hole through the length of the upper part of the piece is to 



33 



24 BLUEPRINT READING 

be drilled and reamed a part of the way and drilled and tapped 
eighteen threads per inch for the rest of its length. Another 
important item is that, while the radius of the hub is given as 
Ys inch, the frame back of the hub is machined back to a radius 
of f inch. 

In the right end view, the things which the, machinist should 
especially note are that one end of the lower hub is marked /, 
while the opposite end is marked "disc grind", indicating that the 
f end is to be carefully finished to an accurate bearing, while it is 
not necessary to be so particular with the opposite end. The end 
view also shows that the hole in the hub is to be drilled and reamed. 
The hole just above the hub is to be drilled and tapped for a 
3%-inch screw, eighteen threads per inch. 

PLATE VII 
CENTER REST BASE 

A reader of this text who is familiar with machine work 
knows that a center rest is a fixture used in turning or grinding to 
give support and steadiness to long or slender work. Plate VIII 
gives a complete view of a center rest and indicates its use and, 
before taking up a study of Plate VII, it will be well to glance at 
Plate VIII. 

The lettered title of Plate VII states that it is the blueprint 
of the center rest base. One is required and it is made of cast 
iron. The piece of work shown is then the mate of that shown 
in Plate VI and some of its features and dimensions are the 
same. A complete front view and "a complete right end view are 
given as well as a portion of a top view, which is placed directly 
above the left upper corner of the front view. 

The working lines of the bottom of the front view and the 
end view show that the base is provided with a, squared projection 
used to locate the center rest on the bed of the machine. Aside 
from this, the machinist should notice the data which relates to 
finishing the small hub at the top of the end view and at the 
upper right corner of the front view. The term "spot face f" 
indicates that the surface touched by the arrow point is to be 
finished, by using a counterbore | inch in diameter, to the limiting 
thickness given just above the end view. It should be noted that 



31 




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1- C.I. 



4--Z7-I7 PART | TICKET 

42? '' 7 THE TAFTPtERCE MF6. COMIKNY. WOASOCKET. R.I. Ui 



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BLUEPRINT READING 25 

certain of the holes are drilled and reamed while others are drilled 
and threaded with a tap. The machinist should carefully observe 
on which of the working lines of the views the / mark is placed. 
He should also note in Plate VII, as in Plate VI, that many of 
the dimensions are given to or from horizontal or vertical center 
lines and that all dimensions bear a certain relation to a common 
center, or axis, A. In reading the dimension figures, the machinist 
will find that several of them have a limiting error tolerance telling 
him that he must be especially accurate in those dimensions. 

PLATE VIII 
CENTER REST ASSEMBLY 
Plate VIII shows two views, and the lettered title placed just 
below the views states that the piece is a center rest assembly. 
The two views furnish a line picture of the completed center rest 
and show all its separate parts as they are when assembled or, as it 
is often termed, set up. It will be noted that each and every part 
is given a number. These numbers are known as the piece, or 
part, numbers. 

PLATE IX 

WORK SPINDLE SLIDE 

Compared with many of the blueprints shown, Plate IX, 
showing the work spindle slide, is difficult to read and it has been 
selected to illustrate a fairly complicated and irregularly shaped 
piece. As an aid in reading this blueprint, a short study should 
be made of the general form and shape of the piece as shown in 
outline in the front, right end, and top views. An examination of 
the views shows that the piece consists in general of two hubs, or 
cylinders, with holes through their length. The cylinders are 
placed with the smaller above the larger and are connected by a 
short web running their entire length. When the reader clearly 
sees this and has the picture clearly in his mind, he can then 
study the various small hubs, bosses, and other pieces attached to 
the two long hubs and their connecting flange. 

In tracing the location and shape of the several parts, holes, 
etc., it should be kept clearly in mind that each part in the front 
view, if shown in the top or in the end view, will be squarely 
above or squarely to the right of its position in the front view. 



^5 



26 BLUEPRINT READING 

Another thing which aids the reader in getting a picture of the 
piece in mind is its name, "work spindle slide." The note just 
over the name plate, "Scale Half Size," of course applies to the 
original blueprint only and not to the reproduction in this text. 

Several helps in the form of lettered notes are on this blue- 
print. As an example, attention is called to a note at one end 
of the front view which tells us that the dotted lines on which the 
arrow points touch represent oil grooves J inch wide and A inch 
deep. From a study of the upper part of the front view and 
of the end view we learn at which points the oil grooves start and 
also that they are drilled at an angle of 45 degrees to reach 
the surfaces of the slide bearings. 

Among the specially important things to be noted is that, 
while the hole through the length of the smaller of the two long 
hubs is a straight plain cylindrical hole, the hole through the 
larger is tapered at its right-hand end J inch to the foot for a 
distance of oh inches. Attention is also called to the two slide 
bearings on the rear side of the work, one slide bearing having right- 
angle sides and the other a 60-degree side. Threads per inch on 
blueprints at the shops of the Brown & Sharpe Manufacturing 
Company are invariably given by Roman numerals. For example, 
as may be noted on the blueprint, a hole threaded fourteen threads 
per inch is marked XIV. Also, each surface which is to be 
finished is indicated by drawing a brilliant red line close beside the 
working line which represents the surface. On this plate and on 
Plates XII and XIII these lines are shown dotted and are drawn 
close to the finished surface lines. Lettered notes placed on this 
blueprint state what special tools should be got from the tool 
room before starting the work. 

PLATE X 
DRAWINQ=IN BOLT 

Plate X shows a drawing-in bolt, and the lettered note just 
below the name tells us that one is required, that the material is 
cold rolled steel, that it is a forging, that it is forged on a heading 
machine, and that it is to be casehardened as shown. The fact 
that the forging is done on a heading machine indicates that the 
head end only is upset to its rough shape. The letters C.II. 



36 



nao mis dook aeen 



■ 




D2AWIN6 IN BOLT 

A2278 A, B.C. FORGIb 
n EN A5 SHOWN. 
' HEADIN6 MACHINE. 



SYMBOL A 2278 A A= 25; 



A 2278 B A' 29 



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A 2278 B 
A 2278 C 


D1A. 
DIA. 


LONG 
L0N6 








TIME. | A2278 


lLOTi 




C2, C3, C5. 

DRAWING IN 

DATE APRIL 25 1917. A. 
BROWN & SHARP E 


BOLT 

°.D. ZY..R.S.L 
MFG. CO., 


(D 


PROVIDENCE, R. 


I- 




A2278 


m?. 





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BLUEPRINT READING 27 

placed just below the threaded end and just below the f-inch 
hexagon end show that the bolt is to be casehardened at these 
places, according to the lettered notes. One view only is given, 
which indicates that an end view would show circles unless other- 
wise specified. A note at the extreme left end of the view states 
that the end is made a j-inch hexagon. 

All length dimensions are easily read with one exception, that 
of the over-all length, which is represented by the capital letter A. 
Notes lettered on the blueprint at the lower right-hand corner 
inform us that, when this bolt is made for and used on C2, A is 
25| inches in length, and when it is made for and used on C3, A 
is 29jf inches. While all the diameter dimensions are easily read, 
the machinist should surely note that several of them have let- 
tered notes giving additional information. For example, we read 
that the yf-inch diameter is to be ground 0.001 or 0.002 inch 

small, "Gr. I ' 9 >S." In this blueprint, the letters Rad. are used 

instead of the capital letter R. to denote a radius. 

PLATE XI 
KNEE SHAFT CLUTCH 

The title plate at the lower right of Plate XI tells us that the 
piece of work shown is a knee t shaft clutch. Further information 
given on the title plate indicates that this clutch is used on A3, 
AA3, BBH2, etc. A lettered note placed on the blueprint just 
below the two views states that the knee shaft clutch is to be 
made of machinery steel, that the rough stock is a piece measur- 
ing 2y&"X2yq", and that a certain formed tool is used by the 
machinist. All the length and all the diameter dimensions are 
easily found and read, while a copious use of notes gives the 
machinist much special information. For example, a lettered note 
placed just below the front view tells us that a certain hole is 
drilled in position after the piece is taken from stock. This indi- 
cates that when finished by the machinist to be placed in stock, 
this hole is left off and that when the setting-up man gets the 
piece from the stockroom, he places it in position and then drills 
it in place. Before starting work on this piece, the machinist 
should read all notes. The front view is a complete section. 



37 



28 BLUEPRINT READING 

In this blueprint, the information concerning the clutch teeth 
is contained in a small view placed somewhat above the front 
view and named a "development of clutch teeth." This view 
represents the outer surface of the clutch teeth rolled out on a 
flat surface, as explained in "[Mechanical Drawing," Part III, 
page 107. The note tells us that the spaces between the teeth are 
0.005 inch wider than the teeth. The view also shows that the 
sides of the teeth slant to an angle of 5 degrees. The end view is 
sufficiently complete to show the form of the clutch teeth only, a 
lettered note placed just below the view giving the number of clutch 
teeth as eleven. As both views show that the piece of work is by 
construction finished all over inside and out, no finish needs to be 
indicated. 

PLATE XII 
BACK TOOL POST 

The title plate informs us that the piece shown in Plate XII 
is the back tool post and that there are a set of tool posts. A 
lettered note placed at the upper right tells us that the tool post 
material is M.L and that it is to be casehardened to have a 
mottled surface. This plate, like Plate IX, lists up the special 
tool-room tools for the job. The views given are front, top, and 
end views supplemented by a small section view, placed just above 
the right end view, showing a section on line A-B. 

This small A-B section shows that the bottom of the large 
slot running through the tool post is at an angle of 5 degrees with 
the back surface of the slot. The working lines of this slot, as 
shown in the front and the end views, indicate that the top sur- 
face of the slot is parallel to the top surface of the tool post and 
that the lower, or bottom, surface of the slot makes an angle of 
20 degrees with a center line drawn parallel to the upper surface 
of the slot. Working lines, drawn as full lines in the front and 
the end views but dotted in the top view, show a projecting 
feather on the under side of the tool post base. Clearly defined 
dimension lines and figures give the width, depth, and length of 
the piece. The machinist should note that the width is to be 
made standard 0.001 inch small; also that certain base surfaces 
are to be surface ground. 



38 



II 









II 




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UNTERBORE FOR 5CREW5 
W #2 TAPER PIN •-C.H. 




ill A2. AA2, Biz, b 
\A\. AAll BBI. BBI 





CENTRE ARM HEAD (COMPLETE) 

DATE JUNE 18 1917 t7. A. EX. A.H.C. 

BROWN & SHARPE MFG. CO.. /"T^ 

PROVIDENCE. R.I. 1 , 






N 


A23I3 (Mf ffff 







BLUEPRINT READING 29 

PLATE XIII 

CENTER ARM HEAD 
t 

Plate XIII is in some respects similar to Plate IX. In read- 
ing this plate, the machinist should first strive to get a general 
picture of the piece well fixed in his mind. As an aid to this, he 
will first note that the work, a center arm head, consists of two 
principal hubs separated by a web or shank to give a center- 
to-center distance of 7| inches. The upper hub is simple, having 
as it does a plain hole through its length and a binder boss on its- 
upper side to be drilled, tapped, and counterbored for a binder 
bolt. The lower hub, however, is well surrounded by projecting 
parts which, as they carry several holes and other finished sur- 
faces, decidedly present difficulties to the reader. He will do well 
to take up each hole as shown in the end view and study each as a 
single hole, getting its position located in each view. 

The larger hole, it will be noted, passes entirely through the 
main lower hub. The hole placed slightly above this hole and to 
the right hand of the end view can, by studying the front view, 
be seen to pass entirely through its hub from end to end. The 
upper hole of the three shown to the left of the main lower hole 
will be found to be placed on a center line with the one just 
noted. A small cross-section view just above, lettered "section 
A-B," aids the reader in clearing up the details of this hole and 
the two similar lower holes; he should carefully note where the 
section line A-B is drawn on the end view. A study of the front 
view and of the section view shows that the upper of the three 
holes passes entirely through the casting from end to end. A 
study of the two lower holes in the end view shows that they 
break into each other. Their location in the front view and in 
the small section view indicates that, while the hole farthest to the 
left passes entirely through the casting, the other, which cuts into 
it, is only 1J inches deep. Extensions of the centers of these two 
holes show by dimension figures that their center-to-center dis- 
tance is ff inch, and a radius line just below the end view shows 
that the center of the outer hole is 2J-inch radius from the center 
of the hole in the main lower hub. 

Diagonally drawn dotted lines in the end view represent a 
hole coming in from the front of the casting at an angle of 22 



39 



30 BLUEPRINT READING 

degrees 35 minutes. In the front view this hole and its boss show 
at the side as a series of full and dotted circles. A lettered note 
placed on the end- view at the right of the vertical center line of 
the view states that an oil hole is to be drilled. Following care- 
fully the lines which represent the oil hole, the reader will find 
that it is to be drilled at an angle of 17J degrees with the center 
line of a similar ^-inch hole showing through the lower side of 
the main hub hole. Further examination of the end view draws 
attention to two small circles at the sides of one of the f-inch 
holes. A study of the small section view shows these circles to 
represent holes drilled, tapped, and counterbored for screws H 
having a f-inch filister head. A radius arc drawn from the hole 
beside which these screw holes are placed shows that their centers 
are placed at j^-inch radius. Other screw holes, oil holes, and pin 
holes can easily be located by a study of the views. In reading a 
blueprint such as this, especial care must be used in locating all 
center lines, radius lines, extension lines, dimension lines, and lines 
showing angles. 

PLATE XIV 

BRASS GLOBE VALVE 

Plate XIV shows a l|-inch brass globe valve and the original 
blueprint is made to full-size scale. Two views only are given. 
The front view shows the valve sectioned as if cut down through 
and on the center line, thus clearly giving an inside view of the 
valve. The end view gives an outline of the valve and is in a sense 
a picture of the valve. The arrangement of the cross-section 
lines in the front view indicates that the sectioned metal parts of 
the valve are, with the exception of the cast-iron handwheel, brass 
throughout. By means of the outline view and the section, the 
draftsman has not only shown all the necessary dimensions of the 
valve as an assembly but has also shown those of each detail so 
well that the machinist can work it out. While it is not general 
practice in shops to have the workman work from assembly blue- 
prints, it may well be done when a shop is building a standard 
article. As there are no finish lines nor / marks, the workman 
would have to decide for himself what surfaces should be finished, 
if given this drawing to work from. 

The several parts of the valve as shown on the blueprint are 



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NAME DRAWING ' AS5£ >"BLED CONE GEARS | Kml 


USED ON 2-3-4-5-PA.UA-2-3-4-VA. 2(/#6rP/f- 3PM 


DRAWN B 


Y O.W. DATE. KB.PS.09 MAY 25, 10. 


| NO WANTED 


CHECKED 


*$■£■ THE CINCINNATI MILLING MACHINE CO 


'BEBHill 


PART 
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SUPERSEDES 


APPROVE! 
REMARKS 


>by CINCINNATI. OHIO. 



15713 



BLUEPRINT READING 31 

the ' valve body, consisting of a globular shaped casting with 
threaded hexagon ends into which, on its upper side, is screwed 
the valve cover casting with a threaded bearing for the long 
spindle; and an upper part, consisting of a stuffing box for the wick 
packing. At the extreme upper end of the stuffing box are a 
small circular gland and a gland nut to force it along the valve 
spindle to compress the wick packing into the stuffing chamber. 
The valve spindle has on its top end a squared taper end to fit the 
cast-iron handwheel and a threaded hexagon nut to hold the hand- 
wheel in place. Toward its lower end an enlarged part of the 
valve spindle is threaded with a rather coarse-pitch Acme thread 
to fit the threaded bearing in the valve cap. The extreme lower 
end of the valve spindle is enlarged and finished to carry the valve 
disc which seats itself on the valve body seat to close the flow 
through the valve body from end to end. The disc, or upper, 
seat moves up and down in narrow guides, as shown in the front 
section view, and a lettered note placed just below this view states 
that these guides are to be bored 2^- inches in diameter. The 
disc has in its lower, or seat, side a circular recess, Iff inches out- 
side diameter by 1^ inches inside diameter, for a fiber, leather, 
asbestos, or other seat ring. Two dotted lines about yq inch apart 
drawn diagonally across the inside of the valve body, as shown in 
the front view, represent a diaphragm rib. This is an interesting 
blueprint to read, as it is necessary to locate carefully all the 
extension lines to learn which working lines they extend. Care 
must also be taken to determine which lines many of the arrow 
points exactly touch. 

PLATE XV 
ASSEMBLED CONE GEARS 

Plate XV illustrates a method of using an assembly drawing for 
shop purposes. The view shows a cone of four gears in section on 
a shaft. The arrangement of the cross-section lines indicates that 
the gears are made of machinery steel. As shown, the whole cone 
of gears is mounted on a steel sleeve which, in turn, runs on a 
composition sleeve. The whole combination is held in position on 
the shaft by steel collars having hexagon-head set screws. As is 
customary in such section views, the shaft is not shown sectioned. 



41 



BLUEPRINT READING 

Its ends, however, are shown as if broken off and the arrangement 
of the section lines at the break indicates that the shaft is of steel. 
Immediately below each gear, as shown in the view, are 
placed the letters A-B-C-D. The first column of a lettered table 
placed in the upper right-hand corner shows that similar cones of 
gears are used on machines, size 2, 3, 4, and 5. The next column 
gives the number of teeth and the pitch of the teeth required in 
the gears A-B-C-D for the various sizes of machines. The 
remaining columns of the table give the outside diameter of each 
gear and its width of face. From this single section view, supple- 
mented by the lettered table, the machinist should be able to get 
all the essential information for making these gears, with the 
exception of the hole diameter, which is not given. The two 
smaller cone gears are shown as if made from a plain steel blank, 
while the two larger gears plainly show that they have a distinct 
hub and rim with a thin web connection. 

PLATE XVI 
FACE GEAR 

The two views of a special face gear shown in riate NVI are 
half size in the original blueprint. The term "face gear'' indicates 
that the piece represented is the large driving gear on the main 
spindle of the machine. While no finish / marks are found on 
the working lines of this blueprint, the average machinist would 
know that the outer diameter, the ends of the hubs, the holes 
through the gear, and the sides of the rim should be carefully and 
well finished. In addition to this, a lettered note at the upper 
right of the front view states that the surfaces indicated by the 
arrow points are rough turned. The title plate informs us that 
one is required and that the material is cast iron, which is also 
indicated by the arrangement of the cross-section lines in the 
front view. 

The view looking toward the end of the gear hub shows that 
the upper small hub has a short supporting flange and that on its 
lower edge the upper hub is counterweighted. A lettered note 
placed just at the left of the front view tells us that the hole in 
the hub is keyseated £f inch deep and | inch wide and that the 
ke\ is dovetailed and drives into place. Both views show the key 



42 




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BLUEPRINT READING 33 

in place. Another important lettered note states that there are 
eighty-seven teeth milled into the outer face of the piece and that 
they are to be six pitch. The workman should especially note that 
the over-all diameter is to be held to definite limits of tolerance. 

PLATE XVII 
DOWN=FEED WORM 

The upper title plate states that the piece shown in Plate 
XVII is a down-feed worm for a 5-foot boring mill. One is 
required and the lower title plate gives the material as machinery 
steel cut from 3f-inch rod 13| inches long, rough dimensions. 
Two views are given, with the front view sectioned to indicate 
steel. All dimensions are given on the front view. The end view 
is sufficient to show that in general the piece has circular outlines. 
The end view also shows the shape of the two keyways and, while 
no direct dimensions are given, this view shows the general position 
of the holes mentioned in the lettered note, "\" drill-J" deep- 
2 holes-drill in position". 

In considering this piece of work, the machinist is, of course, 
first concerned with the reamed l|-inch hole through its length. 
After this hole is finished ready for the mandrel, he should care- 
fully read all the notes and other lettered directions before begin- 
ning to square up and turn the piece. He should especially 
observe what surfaces are to be ground and give careful attention 
to the finished dimensions. He will note that certain dimensions 
have a small limiting tolerance given in thousandths of an inch. 
He should also note that, while the fine-pitch thread shown on the 
right end of the front view is a right-handed thread cut to suit a 
certain nut, the coarse-pitch 29-degree worm thread is to be cut 
left-handed. All dimension lines, figures, and extension lines are 
very clear and are easily located in reference to their working 
lines. The lettered notes have clearly defined arrow points to 
indicate the surfaces to which they refer. Attention is called to the 
diameter dimension reading "2^f inches neck". This shows that 
the piece is to be necked in to this diameter previous to grinding 
the 2 3%-inch diameter as a protection to the corner of the grind- 
ing wheel* No finish / marks are shown, as the piece is finished 
all over, and this fact has been indicated by the initial letters 



43 



34 BLUEPRINT READING 

F.A.O. placed just below the front view. The ^-inch hole show- 
ing just to the left of the flange collar should be drilled before 
cutting the keyway to give a clearance for the cutting point of 
the key seating tool. 

PLATE XVIII 
SADDLE ADJUSTING LEVER 
Plate XVIII, an assembly blueprint, is for the use of the 
setting-up machinist and clearly indicates how the group of parts 
which make up the saddle adjusting lever are assembled. It will 
be noted that each pin, cap screw, set screw, spring, lever arm, 
sleeve, etc., is given a part number and that an arrow point 
clearly indicates the part referred to. The arrangement of the 
cross-sectioning lines in the top view clearly indicates the material 
of each part; for example, they show that the lever arm #1424-9 
and its hub are cast iron, while the handle screwed into its upper 
end is of steel. While the shape and position of each part of this 
mechanism are clearly shown in this blueprint, no dimensions are 
given, which shows us that, as previously stated, the print is to be 
used in the shop only by the assembler. The reader in studying 
this blueprint should consider that he is to assemble the various 
parts and endeavor to decide in what order they should be 
assembled: for example, it is clear that #20197, 02.268, and 20180 
must be placed in position in #14249 previous to screwing #20196 
into it; also that #14249 must be placed in position on #14248 
previous to attaching cover plate #14240. 

PLATE XIX 
TOP PULLEY BRACKET 

The top title plate informs us that the several views shown in 
Plate XIX are of a top pulley bracket for a 5-foot boring mill and 
that two are required. The lower title plate states that the mate- 
rial is cast iron. The views are a front view, a right side view, 
and a top view, which is in this case projected and positioned just 
above the right side view. The arrangement of full and dotted 
lines indicates that the piece consists of a hollow base, or pedestal, 
having at its upper end a shaft-carrying box, or bearing, which, in 
turn, has a large grease, or oil, pocket on its upper side. 



44 



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BLUEPRINT READING 35 

In reading this blueprint, the machinist should observe that 
many of the dimensions given are for the use of the pattern maker 
and are of no especial concern to him. The pattern maker, on the 
other hand, is concerned with all the dimensions as he must add 
sufficient stock to every surface marked with an / to allow excess 
metal for the machinist's purposes. As an instance of this, take 
some of the dimensions as given on the front view and the right side 
view. We observe that at the extreme right hand of the side view 
a dimension of 14 inches is given from the lower line, or base, of the 
pedestal bracket to the center line of the box. While this is a 
dimension for the machinist in particular, the pattern maker must 
also note that the base surface is to be finished and make the 
dimension enough longer than 14 inches so that the machinist will 
have metal stock sufficient to allow him to finish the base surface 
and still have the correct dimension. Also, in considering the 
shaft hole given as 3| inches ream, the pattern maker must make 
his core prints and core boxes enough less than 3f inches in 
diameter to allow stock for machining the hole to the specified size. 
The pattern maker only is- concerned with the dimension \ inch 
given for the wall thickness of the hollow pedestal and that of 9J 
inches given at the bottom of the side view for the width of the 
pedestal. These and many other dimensions are not subjected to 
any machining. The pattern maker, then, in reading this blueprint 
will carefully consider each and every working line, whether 
drawn full to represent a visible outside surface or drawn dotted 
to represent an invisible inside surface, in order to give himself a 
clear mental picture of the construction not only of the outer out- 
lines of the piece but also of all the interior outlines. When the 
pattern maker has this clear mental picture of the piece, he can 
then readily trace the dimensions of all parts of his construction 
by following the extension lines. 

If the pattern maker has fully understood the views up to this 
point he clearly sees: (a) that they represent a ring oiling pedestal 
bracket with the base cored out to leave walls \ inch thick, the 
cored portion to extend up from the base line of the bracket to 
within \ inch of the bottom surface of the cored oil chamber; 
(b) that the cored oil chamber is 4J inches in length in a direction 
across the shaft bearing and If inches in width along the shaft 



45 



36 BLUEPRINT READING 

hole, and that the oil chamber extends out toward the front of the 
bracket into a rounded-end projection, or lug; (c) that he must 
provide a loose pad on the front of the pedestal, as shown, "for 
belt drive only"; and (d) that the bottom surface of the bracket, 
the entire hole through the bracket box, the upper surfaces of the 
oil pocket, and the front face of the bracket pad are to be machined 
as indicated by finish / marks, and that excess stock for machining 
off must be allowed on such surfaces. 

The machinist in reading the views should carefully note 
which surfaces are marked with the finish mark for machining. 
Starting at the pedestal base, as shown in the front and the side 
views, he will observe that its lower surface is to be machined and 
that certain holes are to pass through it. A study of the top view 
and its lettered notes shows that there are to be three holes through 
the base in each of its ends. Two of each three are drilled for 
holding-down bolts and one for Xo. 8 locating taper pins. The 
holding-down bolt holes are to be spot faced for the heads of 
the bolts. 

Returning to a study of the front and side views, the 
machinist notes that the front surface of the pad is to be 
machined. This surface, as shown in the side view, is 4f inches 
from the vertical center line. Four f-inch tapped holes are to be 
drilled into the face of the pad 3} inches apart along the horizon- 
tal distance and 2§ inches apart in the vertical dimension. Before 
machining the shaft bearing shown at the upper part of the front 
and the side views, the machinist should note: (a) that the bear- 
ing proper extends in length from the inner edge of a narrow cir- 
cular oil-collecting pocket to the inner edge of a similar opposite 
circular oil-collecting pocket and that this bearing surface is bored 
and reamed to a diameter of 3| inches; (b) that outside of the cir- 
cular oil-collecting pockets, the hole diameter is increased to 3^ 
inches; (c) that while the circular oil-collecting pockets are marked 
f and are therefore to be machined, no dimensions are given, this 
indicating that they are simply machined to remove the original scale 
and to make them truly circular; and (d) that a large central oil- 
containing chamber is provided for an oil-conveying ring and that 
two oil-return holes are drilled from the edges of the two circular 
oil-collecting pockets at an angle which allows them to enter the 



46 




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BLUEPRINT READING 37 

central oil-containing chamber, the letterea note stating that these 
oil holes are J inch in diameter. Two threaded holes are shown 
through the upper shell of the shaft-bearing box and a note 
attached by a line and an arrow point to the upper view explains 
that they are to be drilled if inch for a J-inch tap. Finally, the 
upper surfaces of the oil box are marked / to be machined. 

PLATE XX 
SHAFT=BEARINQ PEDESTAL 

Plafe XX shows a shaft-bearing pedestal in which the shaft- 
bearing box is a separate unit (not shown) which may be supported 
inside the pedestal. As the shaft-bearing box would be held 
exactly central with the frame of the pedestal, many of the work- 
ing lines of the left side view are drawn around the center line, or 
axis, and several of the dimensions are figured as a radius from a 
common center. The views consist of a front, or edge, view, a 
left side view, and two smaller views, one of which is a section on 
line A-B and the other is placed just below the side view and 
shows a bottom view of the feet of the pedestal. 

Very little machine work is to be done on this piece, merely 
machining the base supports on their under surface, drilling holes in 
the feet for four holding-down bolts, and drilling, tapping, and 
spot facing the three prominent bosses. It will be noted by the 
machinist that the latter holes are at an angle of 120 degrees with 
one another. The machinist should also observe that the base 
supports are to be finished to give their under surface a distance 
of 9J inches from the center line, or axis, of the views. Practi- 
cally all the remaining dimensions are given for the pattern 
maker's use and are easily located and read. 

PLATE XXI 
END SHIELD 

In reading the front view, the small view, and the right end 
view of Plate XXI, the reader should clearly see that when he 
looks at the right end view, he is in fact viewing this end shield at 
its large open end. A study of the front section view shows that 
the casting essentially consists of a large cup-shaped portion at 
the right with only a rim bottom. A half rim is attached and 



47 



38 BLUEPRINT READING 

projects to the left and carries a circular hub having a circular 
hole of two diameters. In this blueprint the machinist, to under- 
stand the views, must carefully follow each working line of the draw- 
ing, locate each extension line, and note each arrow-pointed line. 
All the important finished dimensions are given a limiting tol- 
erance in thousandths of an inch. The rim edge of the large cup 
shown at the right of the front section view is finished to a 5.250- 
inch diameter and 0.094-inch depth; and three holes through the 
rim bottom are also finished. Two of these holes, 4f| inches cen- 
ter to center, are counterbored for fillister-head cap screws, while 
the third hole, showing at the top of both views 2\ inches up 
from the center line, is countersunk for riveting. A detail of this 
is given on the lower side of the blueprint. The circular hub 
which shows at the left of the front section view is machined on 
its outer end and a double-diameter hole is finished through it. 
Four holes are drilled and tapped into the outer face of the hub. 
A lettered note placed slightly to the left and above the hub gives 
the necessary information for these holes. 

PLATE XXII 
ARMATURE HEAD 

Plate XXII is a combined assembly and detail blueprint and 
according to the title plate is made up of (7) armature head 
assembly, (f) armature head, and ® stud (fan-supporting), the 
whole being given the title plate name armature head. The num- 
bers 1, 2, and 3 are clearly shown in the blueprint placed near or 
on the views. The material of the stud is given in the title plate 
as cold rolled steel and that of the armature head as soft steel 
casting. The front view is shown in section on line A-B-C. The 
careful reader will note that section line A-B-C follows the 
vertical center line of the right side view from A at its lower 
edge to B at the center axis and then slants to the right and 
upward, following the center line of one of the three ribs to C. 

Stud. A study of the front and the end views shows that the 
studs (3) (also shown at the upper right of the blueprint) are 
screwed into the three ribs just mentioned, and a lettered note 
placed on the sectioned front view states that they are machined 
to a bevel after assembling. 



48 





SECTION A-B 



FIRST MADE FOR 



ARMATURE END RIN6 

GENERAL ELECTRIC CO., LYNN, MA5L 

DATE OCT. S- 08 343066 



38 

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BLUEPRINT READING 39 

A small detail section A- A placed just over the center of the 
side view shows the form of the slot on the section line A- A 
drawn across the upper edge of the side view. These slots, 
twelve in number, are shown by dotted working lines in the side 
view and are spaced evenly completely around the armature head 
at its extreme left end as the piece is shown in the front view. 

Careful study of the views shows that the armature head 
casting is a circular cup having three narrow shallow ribs cast 
onto the inner side of its rim. It is into the outer ends of these 
ribs that the cold rolled steel studs are screwed, as shown. At 
the opposite, or base, end of the casting is located the outer flange 
for the slots shown in the detail section A- A. Extension lines 
drawn from the working lines of the flange carry a dimension line 
and arrow points which show that the flange diameter is 4j 
inches. The body rim of the casting is to be finished to an out- 
side diameter of 4J inches. The hole through the hub of the cast- 
ing, it should be noted, is finished to a diameter of 1 .375 inches, with 
a tolerance of but one-half of one-thousandth inch above size and 
no tolerance below the figured diameter. The keyway is figured in 
the side view as being \ inch wide and -£± inch deep. It must be 
noted that the keyway is located in the hub hole on the center 
line of a rib and not in the thinner part of the hub. The reader 
should observe that the radius of the rim side of the 4f-inch flange 
is curved to a f-inch radius as shown at the upper left of the 
front view and that a corresponding radius of \ inch for the flange 
slots is shown at the lower left of the front view. The centers for 
'these radius lines are shown as 2 inches from the center line of the 
piece and \ inch from the edge of the piece. A lettered note 
placed just below the side view gives the tapped stud holes as 
14-24 tap-3 holes. The hole in the outer end of the stud is given 
as 10-32 tap-f inch deep. 

PLATE XXIII, Nos. 1 and 2 

DETAILS OF TYPICAL ARMATURE PUNCHINQS 

General Data. Plate XXIII is made up of two D-size prints, 

each giving the details of a separate piece. For convenience in 

referring to them they have been given the numbers 1 and 2. 

Two other illustrations of a like construction are shown in Plate 



49 



40 BLUEPRINT READING 

XXIV. The pieces represented are punchings from sheet steel 
or sheet copper. The reader will note that a single complete 
view of each piece is shown supplemented by section details. 
The complete views, with the exception of blueprint No. 2 on 
Plate XXIV, are drawn to one-half scale in the original blueprint 
and the detail section views, in the original, are made to an 
enlarged scale about double size. These enlarged details show 
the form, size, and kind of holes to be made near the outer 
edge of the punching, as shown at the right of the complete 
views. A lettered note resting on an arrow states that there are 
to be eighty-three holes equally spaced around the punching. 

Armature End Ring. The title plate gives blueprint No. 1 as 
an armature end ring punched from hard sheet copper 0.125 inch 
thick. The holes and the entire punching are made by using 
what is known as a perforating and shearing punch and die. The 
metal punched out of the hole, in this case, is turned, or bent, 
inward as shown in the enlarged details. A note with two arrow 
pointers tells us that this punching has two iV-inch saw cuts. 

Armature Punching. Blueprint No. 2 is an armature punch- 
ing punched from standard quality soft sheet steel 0.014 inch 
thick. A single view shows the complete punching. It has a 
7-inch hole of a maximum tolerance of 0.001 inch above size and 
the outside diameter is 10.960 inches with a minimum tolerance of 
0.006 inch. The punching is provided with a keyway § inch wide 
and H inch deep. The outer rim is provided with eighty-three slotted 
holes equally spaced around the circumference. An enlarged view 
of these slots is placed just to the right of the complete view. * 
Lettered notes with arrowhead pointers give all the slot dimensions. 

PLATE XXIV, Nos. 1 and 2 
DETAILS OF TYPICAL FIELD PUNCHINGS 
Field Punching. In Plate XXIV are shown two blueprints of 
which No. 1 is a field punching punched from soft sheet steel, 
standard quality, 0.014 inch thick. One complete view only is 
given but, as in the blueprints shown in Plate XXIII, there is an 
enlarged view of the slots. This enlarged view gives complete 
details of the slots and the exact dimensions with all limiting tol- 
erances. A note placed below the complete view tells us that the 



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BLUEPRINT READING 41 

slots are thirty-six in number. The punching has four lugs on 
its rim placed 90 degrees apart. The outer contour of each lug, 
the careful reader will observe, is made up of arcs of circles con- 
nected by short straight lines drawn tangent to the arcs. This gives 
an irregular outline to the lugs. The die maker will, of course, 
note that many of the dimensions for this punching are exact to 
quite small limiting tolerances. 

Pole Piece Lamination. Blueprint No. 2 is a pole piece lam- 
ination, and the upper note informs us that it is punched from 
sheet steel, common quality, 0.0625 inch thick. When the reader 
considers the thickness dimensions of the punchings shown in 
Plates XXIII and XXIV, he will readily see why an edge view is 
not given except at an enlarged scale, as in the several detail 
views. Plate XXIV, No. 2, is drawn full scale in the original 
blueprint. Only two dimensions show limiting tolerances. Most 
of the radius lines are from a common center placed somewhat 
above the view and on its center line. Centers for the other 
radius lines are clearly defined by small circles inclosing the center 
points. Radius lines are clearly drawn and dimensioned with the 
arrow points touching the working lines of the view. The die 
maker should carefully locate that part of the working line to 
which each radius line refers. 

PLATE XXV 
GEARS USED ON 12=INCH MERCHANT MILL 

The title plate tells us that Plate XXV shows gears used on a 
12-inch merchant mill. The bill of material states that one of 
these is made from steel casting thoroughly annealed and the other 
from an open-hearth steel forging. In the original blueprint the 
views are drawn to a scale of 6 inches to 1 foot. Where two 
gears are shown and one is larger than the other, the smaller of 
the two is the pinion and the larger is the gear, and in reading 
this blueprint they will be referred to in this way. 

The pinion is shown in two views, with the front view in sec- 
tion as if sliced through the center of its length. The end view 
at the left of the front view clearly shows the hole and its keyway 
through the pinion; other than this, it consists of three concentric 
circles representing the outside diameter, the pitch diameter, and 



51 



42 BLUEPRINT READING 

the root diameter of the pinion teeth. A lettered note placed 
just beneath the views tells the machinist that the pinion is to 
be hobbed and has twenty-four teeth of the regular 14|-degree 
involute form, five diameter pitch. The term diameter pitch refers 
the pitch of the teeth to the pitch diameter of the gear. Finish / 
marks show that the pinion is to be finished all over. 

The views of the gear are arranged similarly to those of the 
pinion. Finish / marks show that the ends of the hub, the sides 
of the rim, the outer diameter of the rim, and the hole through 
the center are to be machined and that the inside of the gear rim 
on both its ends is chamfered as shown. The machinist should 
carefully note that the hole through the hub is bored 3J inches in 
diameter and that the gear is to be forced onto its shaft with a 
pressure of 18 tons. The machinist should also observe that there 
are forty-eight 14|-degree involute teeth in the gear and that they 
are to be cut on a gear-hobbing machine. The pattern maker 
should especially note that there are six holes cored through the 
web of the gear. All dimensions and extension lines are clearly 
and plainly defined and so placed as to be easily read. 

PLATE XXVI 

BEVEL GEARS FOR ROLLS ON SHEET BAR AND SLAB=MILL 
STEAM FLYING SHEAR TABLE 

The title plate of Plate XXVI informs us that the views 
shown represent a pair of bevel gears used on a 21-inch sheet bar 
and slab mill steam flying shear table. The bill of material shows 
them to be open-hearth steel castings thoroughly annealed. The 
front view of the gears is sectioned by a plane along their axes 
and shows the gear and the pinion with their teeth engaging, or in 
n/rs-h as it is called. A pair of bevel gears are usually shown thus, 
and the reader should make himself familiar with this fact and 
should study every detail. The end view of the pinion and the 
end view of the gear are just sufficiently complete to show the 
hubs and the holes and key ways through the hubs. 

A lettered note A states the number of teeth in the pinion, 
the form of the teeth, the pitch of the teeth, and how they are to 
be machined. A lettered note B gives like information for the 
gear. When reading these lettered notes, the machinist should 



52 





J B 23162 XXVI 



MORGAN CONSTRUC 



B 23162 



42 

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BLUEPRINT READING 43 

not fail to observe that the gear teeth are 20 degrees involute 
instead of the ordinary 14J degrees, also that the pitch of the 
teeth is given as circular pitch instead of the more common 
diameter pitch. Circular pitch is the distance from the center 
line of a tooth to the center line of the next tooth and is measured 
along the pitch circle. In bevel gearing, it is measured at the 
largest pitch diameter. 

The machinist, after carefully reading the lettered notes, is 
next concerned with the holes through the hubs of the gear and of 
the pinion. He will note that the gear is to be forced onto its 
shaft with a pressure of 15 tons and that in the pinion the hole 
should be a tight fit on the shaft. He will also observe that each 
keyway is to taper at the rate of J inch per foot. The machin- 
ist's next concern is the outside diameters of the gear and of the 
pinion. By following the extension lines to their dimension lines 
he learns that the gear is 14.725 inches and the pinion 9.705 inches 
outside diameter. He then locates the angles which give him the 
cone form of the pinion and the gear blank and notes that they 
are given in degrees and minutes. By using a bevel protractor in 
his measurements he can readily machine the cone sides and edges 
to the required angles as given on the blueprint. Making the 
length of the tooth an even 3 inches as given completes the pinion 
and the gear blanks (so far as the tooth rims are concerned) ready 
for cutting the teeth. The back end of each hub is faced up and 
its end circumference is machined into a circular groove of definite 
dimensions which are easily found and noted. 

Previous to planing the teeth, the machinist should locate the 
angle marking the bottom of the tooth space. This angle is 
known as the cutting angle, and in this blueprint the reader will 
find it for both gear and pinion near where the center lines of the 
gear and the pinion cross each other. For the gear, the cutting 
angle is 54 degrees 37 minutes and for the pinion it is 29 degrees 
19 minutes. The total depth measured at the outer end of the 
teeth should be noted. This is given as f inch +0.45 inch. As such 
gears as these are usually planed on a special gear-tooth planer, no 
further directions need to be given. The pattern maker will find 
in this blueprint all the necessary dimension lines, radius lines, 
and figured angles for a complete pattern for each gear. 



53 



U BLUEPRINT READING 



PLATE XXVII 



MOTOR COUPLING FOR ROD MILL DRIVE 

Plate XXVII shows the parts of a motor coupling for a rod 
mill drive. The bill of material notes six parts A-B-C-D-E-F 
and gives the material from which each part is made and the 
number of each required. In the original blueprint all the views 
are one-quarter size, 3 inches to 1 foot. Lettered note 1 gives 
special shipping directions, and a most important note placed in the 
center of the end view gives explicit directions regarding the size 
of the hole and states that it is to be shrunk on the motor shaft. 
The front view of the coupling body A is sectioned through the center 
of its length. For the pattern maker, this is a simple job and he 
can make no mistakes in finding his dimension lines and figures. 

The machinist who carefully reads the views will note that 
many of his dimensions are given to a special fixed gage. The note 
on the end view states that the hole is to be bored 0.007 inch 
small to allow a shrink fit. The key way in the side of the hole 
is to be tapered § inch per foot. A note at the hub end of the 
front view shows that this end of the hole is to be chamfered. 

There are two hole keyways if inch deep at the deeper end 
and a broad shallow key way across the face of the flange part of 
the coupling, If inches deep and 3J inches wide to gage. Finish/ 
marks on the working lines of both views indicate that the piece 
is machined all over. The smaller details of the coupling B-C-F 
are given near the right end of the blueprint. F shows two views 
of the key which fits the broad keyway machined across the face 
of the coupling flange; one end of the key is curved, as shown, to a 
radius of 10| inches. A 1^-inch hole is shown drilled near the 
curved end and this helps us to understand that a flange bolt B 
passes through this end of the key when it is fitted in place in the 
face of the flange. The width dimension shows that it is to gage. 
The flange coupling bolts B with their nuts C are shown by a front 
and an end view. The front view shows the nut C in place. 
which is a common way of showing bolts and nuts. A hole is 
shown drilled through the body of the bolt near its threaded point 
for a ^-inch cotter pin. The end view gives the shape of the bolt 
head and nut and .-hows it is chamfered at its outer corners. 



54 



45 



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ATERIAL 

DESCRIPTION 
BINDER ARM 


A 180 59 C 
A.I8059 6 
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A/8059 F~ 
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6 BAR 57. 


PIN S 7 /k,"DIA.X 50%" 16. 
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B 10084 HA 
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21" SHEET BAR 

COOLIN 

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3NTRACT SHARON S.N. CO. 

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BLUEPRINT READING 45 

PLATE XXVIII 
BINDER ARM FOR ROPE TAKE=UP 

The title plate shows that the views in Plate XXVIII are of a 
binder arm for rope take-up used on the cooling beds of a 21-inch 
sheet bar and slab mill. A long bill of materials is given. The 
title also tells us that in the original blueprint the views are drawn 
to a scale of 3 inches to 1 foot. 

The views are complete and this is a very interesting blue- 
print for either a pattern maker or a machinist. For example, the 
reader will note that at the right-hand upper part of the front 
view the bearing cap is shown in place on its bearing by a series 
of dash and dot lines known as broken lines. This gives a sort of 
skeleton view of the cap. At the same place is a skeleton view of a 
bushing marked A18059F. Looking this number up in the bill of 
materials, the reader finds that the bushing is made of lumen 
bronze and that eight are required for four binder arms. Directly 
below this part of the view and at its extreme lower edge, similar 
skeleton views are shown of a cap A18059C and a bushing A18059D. 
In looking for these numbers in the bill of materials, the reader 
finds the names of the parts, the material used, and the number 
required for four binder arms. When the reader has carefully 
located each part in the bill of materials, he should consider its 
name, the number required, and the material used. The bill of 
materials shows that the binder arm is marked A, that it is made 
from a steel casting, and that four are required. 

Another interesting matter relating to this blueprint is the 
method used in sectioning various parts of the views to open up 
the bearings clearly to the reader. A bottom view of the lower 
bearing is shown placed just below the side view and a similar top 
view of the upper bearing is placed just above the left side of the 
front view. The machinist must finish the four bearings to fit the 
caps and the lumen bronze bushings and drill a pin hole 3ff inches 
in diameter for A18070G through the length of two circular hubs 
plainly showing in the lower half of the front and the side views. 
In addition, he must drill a |-inch oil hole in the upper part of 
the lower bearing and a hole just below each of the upper bear- 
ing and tap for a J-inch pipe plug. The machinist will also note 
that both ends of all four bearings and the inner ends of the pin 



55 



46 BLUEPRINT READING 

hubs are finished and that a spring brass wiper is riveted into each 
of the upper boxes near its inner end. 

The pattern maker will note that the framework of the piece 
is a simple rib construction for supporting the several bearings and 
hubs and that the working lines are well dimensioned. 

The upper bearings are complicated by having to be cored for 
an oil well, or chamber. The oil in this chamber is distributed to 
the shaft by means of a tinned steel universal chain A18059Y 
hung on the shaft into the enlarged part of the center of the oil 
chamber. The pattern maker should also note the special cored 
holes through the outer and the inner ribs showing just below the 
long pin hubs. Finish / marks placed across certain working lines 
of the view show the pattern maker for which surfaces he must 
allow an excess of metal for the machinist's needs. The bolt holes 
in the upper bearings for A18059W are cored, while those in the 
lower bearings for A18059V are drilled by the machinist. 

PLATE XXIX 
PARTS JOF SHUTTLE MECHANISM FOR LOOM 

Plates XXIX, XXX, and XXXI are each made up of four 
small blueprints originally 4|"X5J" and show the practice of the 
Crompton-Knowles Loom Company. The small 4|"Xo§" blue- 
prints are those used in their shops as working blueprints. Each 
small blueprint is from a free-hand sketch of some part of one of 
their machines and contains all that the workman needs to know 
when machining the piece. Blueprints made like those which we 
have been studying are used by the pattern maker. 

A number placed in a circle has been added to each small 
blueprint to make it easy to refer to and each is provided with a 
title plate which contains certain information useful to the work- 
man. For example, the title plate of the small blueprint No. 1 tells 
us that the piece is a rocker iron for a shuttle change motion on a 
medium duck loom and that the material is cast iron. Blueprint 
No. - shows the lower part of a shuttle carrier; No. 3, a stand 
for a lifter; and No. 4, the top part of a shuttle carrier. In many 
of these blueprints no over-all dimensions are given, and as they 
are not made to any particular scale of sizes, in such cases the 
-ketch artist places the over-all length of the piece in the upper 



56 



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BLUEPRINT READING 47 

left-hand corner in small numerals over or on a short line; for 
example, the piece in blueprint No. 1 is 21 inches long. While this 
dimension is of no value to the machinist, it does aid the stores 
keeper in handling the castings, for, while each sketch is a picture 
of the piece in so far as its outlines are concerned, unless the 
small numerals are read, there is nothing in the view to indicate 
whether the piece is inches or feet in length. While such working 
blueprints are not commonly used, it is worth the reader's while to 
study them, as they show very clearly the use of free-hand sketches. 
It must be borne in mind that in certain lines of machine 
building, while a given machine may consist of a great many 
parts, each part may be a very simple piece requiring but little or 
no machining; for example, blueprint No. 1 shows a piece of work 
that is to have four drilled holes, two of which are tapped; No. 2 
shows a piece with one drilled hole; No. 3 is marked "no labor" 
and shows a piece of work in which the holes are made in the 
foundry by the use of properly shaped cores; and No. 4 is a little 
more complicated, having two j^-inch tapped holes 3 J inches apart 
and one J-inch tapped hole with the end of the hole boss, faced. 

PLATE XXX 

DETAILS OF GEARED MECHANISM USED ON 
CROMPTON=KNOWLES LOOM 

In Plate XXX, blueprint No. 1, which represents a stand for a 
gear guard, is shown in the same manner as the blueprints in 
Plate XXIX. When pieces are sketched in this way, they are 
said to be shown in perspective; they are also termed picture 
sketches, as they are shown tipped and swung around from the 
regular squarely viewed position of the ordinary blueprint. Blue- 
prints Nos. 2, 3, and 4, Plate XXX, representing a spur gear on 
the crankshaft, a hub for a pulley, and a spur gear on the bottom 
shaft, respectively, are shown viewed squarely from the front, and 
the real difference between them and most of the blueprints which 
we have studied lies in their being made by free-hand pen methods 
rather than by the use of drawing instruments. An end view of 
blueprint No. 2, 3, or 4 would show a series of concentric circles. 
Finish / marks indicate the working surfaces which are to be finished 
by some method of machining. 



57 



48 BLUEPRINT READING 

In Xos. 2 and 4 two dotted working lines and a lettered note 
tell us that a 3^-inch keyway is to be machined in the surface of 
the holes through the central hubs of these gears. In the case of 
Xo. 2, a lettered note states that four ^-inch holes on a 6J-inch 
circle are to be drilled through the web of the gear, and the 
sketch shows that these are placed in slightly raised hubs, or 
bosses. It will be noted by the careful reader that, while in most 
instances the finish / marks are placed in the usual manner on the 
working lines of the views, in some cases they are given with 
the dimension figures. As a case in point, take the. diameter of the 
longer hub in Xo. 2. Here the finish/ mark follows the dimension 
figures thus, 2f" /. Several similar cases will be noted in these 
sketches by the interested reader. While most machine gears 
have "cut" teeth, this is not universally so on certain lines of 
machinery and lettered notes at the top of Xo. 2 and Xo. 4 state 
that these gears have "cut" teeth. 

PLATE XXXI 

MISCELLANEOUS MECHANISMS LSED ON CROMPTON= 
KNOWLES LOOMS 

Plate XXXI, like the two preceding plates, is made up of 
four blueprints originally 4§"X5§". Heading the title plate, we 
learn what each piece is and the material used. Blueprints Xos. 
1, 2, and 4 show, respectively, a stand for a shipper and lock lever, 
an angle iron post, and a guide for a lifter rod, and they are pic- 
ture, or perspective, views. Xo. 3 is the ordinary type of free- 
hand sketch and shows a front and an end view of a ratchet and 
pinion. While no special directions are needed in reading, atten- 
tion is called in Xo. 1 to the f-inch hole near the lower part of 
the piece. While this shows the stud $£757 in place, the stud is 
evidently a separate piece. In Xo. 2, the long shank has no finish 
/ marks but is marked f" /. In Xo. .3 two views are necessary 
to show that one set of teeth is on a slender hub. 

PLATE XXXII 
BRASS CHECK VALVE 
First=Angle Projection. While "Mechanical Drawing," Parts 
I, II, and III, does not analyze in detail the method of projection 



58 



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49 





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BLUEPRINT READING 49 

used in Plate XXXII, readers of blueprints often have such 
placed in their hands. The blueprints of machine parts shown in 
this text are, with this one exception, drawn in what is known as 
third-angle projection. In, addition to what this book contains on 
views and their arrangement, "Mechanical Drawing," Part III, 
defines and illustrates first-angle and third-angle projection and the 
blueprint reader should study the opening pages of Part III. In 
Fig. 97, Part III, the reader will note that the lines of the piece 
viewed are sent forward on a plane surface. In other words, 
instead of placing the object we are viewing on the far side of 
some material l : ke plain glass and viewing it through the glass and 
then making on the glass a sketch of what we see, the object is 
placed in front of the glass and we make the sketch on the glass 
as if we sighted along its edges and drew lines on the glass in line 
with the edges we were sighting. Looking at an object in this 
manner places the right end view in the blueprint at the left side 
of the front view instead of at the right side as in previous blue- 
prints, and the surface lines seen in looking down on the top of 
the object are shown below the front view. 

Placing of Views. If this method is clear in the reader's 
mind, let him return to Plate XXXII. He will observe that the 
front view of this l|-inch brass check valve has been placed at the 
upper left-hand corner of the sheet. Just below the front view 
and centered w T ith it is the view one would get of this valve if he 
were viewing it on its top side, or upper surface. By the regular 
third-angle system of placing views, the top view would be shown 
above the front view. The end view, as the careful reader will 
note, represents the view one w T ould get if looking at the left end 
of the front view. While it is, then, a view of the left end of the 
valve and would, in ordinary view arrangement, be placed at the 
left of the front view, it is by the first-angle arrangement of views 
placed at the right of the front view. In tracing the location of a 
line from one view to another, the blueprint reader will need to 
use care if he is not accustomed to this method of showing views. 

Details of Blueprint. Other than the arrangement of views, 
this blueprint is easily read, having, as it does, a hollow spherical 
body with hexagon ends and a circular hole in its upper side, 
a hexagon cap screwed into the top side hole, and an internal 



59 



50 BLUEPRINT READING 

swing hinged valve flapper. A tapped hole in the upper right 
corner of the body is made at an angle of 40 degrees with the 
axis of the valve body and into this is screwed a special plug as 
shown. The flapper is hinged on a small diameter spindle which 
is centered and held in place by two bearing plugs placed opposite 
each other in the body of the valve. The flapper consists of a 
hinged frame, a circular disc having a ring of leather or asbestos 
in its under side groove, a bolt, a nut, and a w T asher to hold the 
ring in the disc groove and the ring and disc onto the hinged frame. 

PLATE XXXIII 
SPINDLE 

When interpreting Plate XXXIII, the reader will note from 
the title plate that the spindle is made from 15-point machine 
steel. Fifteen point when used in this manner means that the 
carbon content in the steel is fifteen-hundredths of one per cent. 
The shop man and the mill man shorten this by saying or writing 
it 15 point. A front view only is needed to show all the necessary 
outlines of the spindle and to give all the necessary dimensions 
for the workman as an end view would consist of a series of con- 
centric circles except for the keys and their seatings. 

Dotted lines centered with the center line of the work and 
drawn from end to end of the view show a hole through the 
length of the spindle. A lettered note tells us that in the right- 
hand, or nose, end of the spindle this hole is No. 12 taper to a 
plug depth of 6 inches. In producing the hole, the workman 
would first drill a hole 7f inches deep plus or minus f inch, using 
a 1^-inch drill, and then he would continue the hole completely 
through the length of the spindle, using a 1-inch drill. A lettered 
note with an indicating arrowhead informs us that the rear end of 
the hole is to be chamfered | inch for center. Another lettered 
note states that the spindle bearings are to be pack hardened at 
least Ye mcn deep. A lettered note placed near the nose of the 
spindle tells us that the 3|-inch and the 3|-inch diameters arc to 
be a forced fit in part #4470. Sonic makers of working blue- 
prints use the term press fit instead of force fit. Either term 
would indicate that part #4470 is to be pressed onto the spin- 
dle at the places indicated by the arrow points. The lettered 



60 





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BLUEPRINT READING 51 

note placed at the left end of the spindle refers to a wringing fit. 
A wringing fit is one in which the parts are so fitted in dimensions 
as to have to be wrung, or twisted, together; some workmen inter- 
pret this to mean a fitting so snug that the pieces go together by 
lightly rapping them. In any case, it means a fit so snug that a 
little forcing is needed to slip the pieces together. The reader's 
attention is called to the limiting tolerances as expressed by the 
plus and minus signs and to the printed directions placed at the 
lower edge of the sheet which state that "unless otherwise speci- 
fied, limits on this drawing are ±0.005"; dimensions of angles ±1°; 
and reamed or bored holes standard to 0.001" small". The term 
Woodruff key refers to the Whitney system of using Woodruff keys. 

PLATE XXXIV 
ROOF TRUSS 

Plates XXXIV and XXXV are shown for the reason that the 
average shop man may be at times called upon to use such. 
Plate XXXIV shows a piece of structural work known as a roof 
truss. The word "truss" is shortened to Tr. on the blueprint. 
Steel structural work such as trusses, beams, girders, and columns 
is usually made up of angles, I beams, channels, plates, etc., 
riveted in such a manner as to get the desired construction. The 
various angles, channels, etc., are known as shapes and are hot 
rolled at the steel mills, straightened, and sold in open market. 

The truss shown in Plate XXXIV is built up of angles of 
varying lengths riveted together and to flat pieces of plate known 
as gussets, or sometimes gusset plates. The several pieces of 
angles are given a letter symbol. In the roof truss shown the 
short pieces of angle steel used to tie the upper and lower parts 
together are symbolized by D and show on the blueprint as D-l , 
B-2, etc. The gusset plates are symbolized by G and appear on 
the blueprint as G-l, G-2, etc. In many cases a truss is too 
long to ship complete and has to be partly completed at the place 
used, or, as it is termed, in the field, and rivets driven after the 
truss leaves the shop are known as field rivets. The rivets which 
are to be driven while the truss is being built in the shop are 
indicated in the blueprint by small full circles, while the position 
of field rivets is shown on the angles by small white circular spots. 



61 



52 



BLUEPRINT READING 




■THICKNESS 



SHORT LEG' \^ 
Fig. 2. Details of Angle Sections 



Noting what has been said relative to riveting, it will be observed 
that the blueprint shows that this truss is to be shipped in three 
sections and field riveted at the place where it is to be used. 

A steel angle as rolled has the form shown in Fig. 2. The 
upright and the horizontal parts are known as the legs of the 

angle. In the truss shown, 
two of these angles about 30 
feet 10 inches long are placed 
back to back to form the left 
half of the upper slant of the 
truss. In the same manner, 
two angles about 29 feet 11^ 
inches long are placed back to 
back to form the right upper half of the truss. Previous to riveting 
the angles together for making each top slant, gusset plates as shown 
at G-l, G-2, G~4, G-5, and G-7 are slipped between the angles and 
the whole is riveted together. In a like manner, the lower chord of 
the truss is riveted up. It will be noted that the gusset plates G are 
trimmed to come flush at the outer surfaces of the truss, but that 
they project into the inside of the truss a distance sufficient to 
allow the several short angles to be riveted to them. It will also be 
observed that when the angles are riveted together back to back 
with gusset plates, the surfaces of the legs of the angles are sepa- 
rated by an amount equal to the thickness of the gusset G. Any 
rivets driven through the angle plates at space points held apart by 
the gussets have small washers slipped into the crack, or space, 
between the angles, and the rivets are then set up through the 
washer. This is shown on the blueprint by means of a dotted 
circle around the space rivets. It must be noted that the bottom 
chord of the truss is not made up of single-length angles but is 
spliced at points about 15 feet 4| inches from each end of the truss. 
Where a splice such as this occurs in the bottom chord of a truss, 
it is strengthened by riveting a splice plate onto the bottom of the 
angles, covering and tying the splice. 

Instead of giving in degrees and minutes the angle one piece 
makes with another, as is done in machine shop drawings, a 
small triangle is placed on the piece, as shown at the upper end 
of angle D-3 and on its lower side. This means that the line 



62 




53 



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:hes in 
♦hes in 
end of 
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XXXV 




FOUNDRY BUILDING 



52 

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BLUEPRINT READING 53 

on the gusset plate along which the rivet holes are to be placed 
rises from a base line 8ji inches in 12 inches. The layout man 
accordingly measures off a base line on the gusset 12 inches in 
length and erects a perpendicular line on one end 8fJ inches in 
height. From this height he may scribe a line to the other end of 
the 12-inch base line and this is the gage line for the rivet holes. 
In all structural steel work the rivet holes are spaced along lines 
located a given distance from the back of the angle. These lines 
are termed gage lines and are not center lines in the usual sense. 
For example, in the view shown the reader will note that in the 
top member of the truss in the front view there are two gage 
lines and therefore two lines of rivets. 

It will be observed that, while the top view of the truss is 
placed above the front view as in previous blueprints which we 
have studied, it parallels the slant of the truss. If a bottom view 
were given of this truss, it would show as if viewed from inside 
the truss; such a view is distinctly different from the bottom 
views already studied, and this point should be carefully noted in 
reading structural drawings. 

PLATE XXXV 
PLAN OF FOUNDRY BUILDING 
Plate XXXV shows the plan of a foundry building. While 
the blueprint is more than ordinarily complete, it fairly represents 
such plans. The walls of the building are of brick and the win- 
dows are the prominent features of the walls. The reader should 
observe that the outside dimensions of the building, the door 
sizes, and the thickness of the walls are given; the columns, posts, 
interior walls, and partitions are located; the center-to-center dis- 
tances are given; the foundry equipment is given and its position 
located on the plan; all stairways are indicated; and room measure- 
ments are given. Attention is called to the method of represent- 
ing the windows by means of two parallel lines placed across the 
openings in the brick wall and to the method of showing the doors 
swung partly open. The plan shows a gallery floor along one side 
of the building. On this floor are located the office of the fore- 
man, the charging floor for the cupolas, the motor room, etc.; the 
gallery floor is supported partly by the 9-inch latticed channel 



63 



54 BLUEPRINT READING 

columns and partly by a series of 6-inch round cast-iron columns. 
Three sets of doors are shown opening into the air and one open- 
ing into a tunnel to the shop. As a means of carrying off roof 
water and drainage from the pickling bed and cleaning room, a 
soil pipe line is shown. As most of this line of pipe is placed 
beneath the floor, it appears in the blueprint as a double dotted 
line. Two tile-lined chimneys are shown; one of these is for the 
brass furnace and one for the core oven. The core room is partly 
inclosed by means of a low wall capped with cast plates. The 
8-foot door opens onto a driveway as do the two 5-foot 8-inch 
doors. These driveways and the street along the front of the 
building are not shown in the plan, but the street location could 
be assumed by the fact that the soil pipes, the clay drain, and the 
water pipes extend beyond the wall in a certain direction. 

PLATE XXXVI 
TYPICAL FIRE INSURANCE MAP 

In fire insurance work the graphic description of a property 
has an important function; the custom is to show a plan or simple 
diagram of the insured properties, Plate XXXYI, adding certain 
simple devices for indicating such features of the building as may 
conveniently be described in this manner. 

The map of a fire insurance risk gives the general location 
of the risk and its position relative to other risks. It also shows a 
scale drawing of the ground plan of the building, giving the dimen- 
sions, area, and, at the same time, a perfect idea of its general 
contour and the relation of the subdivisions of the building. By 
varying the thickness of the wall lines they are made to represent 
different kinds of walls. Unfinished or incomplete walls are repre- 
sented by dotted lines; open spaces in the line indicate where the 
wall is interrupted or where a window opening occurs. Color is 
used to a large extent to indicate the different forms of construction; 
certain symbols, which follow in a measure the shapes of the things 
they represent, are used to shorten the description; and of course 
the use of initial letters is too well known to be more than mentioned. 
These symbols, it must be understood, are purely arbitrary but, 
having become established and recognized, they form the symbol 
language of the inspector and must be studied in a practical way in 



64 



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64 



1 



BLUEPRINT READING 55 

order to be recognized when presented. A few of these symbols and 
their description are given to convey some idea of the manner in 
which the map may be interpreted. 

A solid thick line — — ^^^— represents an independent wall. 
A solid thin line represents a party wall. A distinct break in the 

line representing a division or side wall indicates 

an opening made by a doorway or arch. A small curved line 

— ' — or a short line at right angles indicates the presence 



of a fire door, the auxiliary line being placed on the side of the wall 
the door is on. An auxiliary line on each side indicates a fire door 

on each side of the walls. A double curved line 



A little 



is used to represent a standard fire door. 

black dot on the inside end of a window line indicates a window 
opening on that side of two adjoining walls. If the black dot is 
missing, it means that there is no window on this floor. A single 
curve over the end of the window line represents a non-standard fire 
shutter. A straight line indicates the presence of wire glass. The 
initial H within a hollow square is used to represent a hoistway 



or hatch. 



S 



The letter S within a hollow square is 



used to represent a stairway. A stairway is also represented by a 

, rectangular outline crossed by straight lines supposed to represent 

the stair steps. A solid black oblong figure represents a horizontal 

boiler, while a solid black circle represents a vertical boiler. A thin 



line around the solid black oblong figure \^BIB and the margin 

60 HP. 

colored in red represents a horizontal steam boiler which is bricked 
in. A small thin-lined circle with diagonals and a black dot at 



their intersection wQas. indicates an automatic sprinkler riser. 

A sprinkler pressure tank is represented thus d D . 

Plate XXXVI is a copy of a map issued in connection with the 
adoption of these symbols by the Fire Underwriters Uniformity 
Association and brings into use practically all the symbols needed. 



65 



MECHANICAL DRAWING 

PART I 



The subject of mechanical drawing is of great interest and 
importance to all mechanics and engineers. Drawing is a method 
of showing graphically the minute details of machinery; it is the 
language by which the designer speaks to the workman; it is the most 
graphical way of placing ideas and calculation on record. A brief 
inspection of an accurate, well-executed working drawing gives a 
better idea of a machine than a lengthy written or verbal description* 
The better and more clearly a drawing is made, the more intelligently 
the workman can comprehend the ideas of the designer. Thorough 
training in this important subject is necessary to the success of every- 
one engaged in mechanical work. 

The draftsman is dependent for his success, to a certain extent, 
upon the quality of the instruments and materials which he uses. 
As a beginner, he will find a cheap grade of instrument sufficient 
for his needs; but after he has become expert, it will be necessary for 
him to procure those of better construction and finish to enable him 
to do accurate work. It is a better plan to purchase the well-made 
instruments, if possible, at the start. 

INSTRUMENTS AND MATERIALS 

Drawing Paper. In selecting drawing paper, the first thing 
to be considered is the kind of paper most suitable for the proposed 
work. For shop drawings, a manila paper is frequently used on 
account of its toughness and strength, for these drawings are likely 
to be subjected to considerable hard usage. If a finished drawing 
is to be made, the best white drawing paper should be obtained, so 
that the drawing will not fade or become discolored with age. A 
good drawing paper should be strong; should have uniform thick- 
ness and surface; should stretch evenly and lie smoothly when stretched 



67 



2 MECHANICAL DRAWING 

or when ink or colors are used; should neither repel nor absorb liquids; 
and should allow considerable erasing without spoiling the surface 
It is, of course, impossible to find all of these qualities in any one 
paper, as great strength cannot be combined with fine surface. How- 
ever, a kind should be chosen which combines the greatest number 
of these qualities for the given work. Of the higher grades of papers, 
Whatman's are considered by far the best. This paper, either side 
of which may be used, is made in three grades: the hot pressed, which 
has a smooth surface and is especially adapted for pencil and very 
fine line drawing; the cold pressed, which is rougher than the hot 
pressed, has a finely grained surface, and is more suitable for water 
color drawing; and the rough, which is used for tinting. For general 
work, the cold pressed is the best as erasures do not show as plainly 
on it, but it does not take ink as well as the hot pressed. 

Whatman's paper comes in sheets of standard sizes as follows: 

Cap 13X17 inches Imperial . . . . 22x30 inches 

Demy ...... 15x20 " Atlas .... 26X34 " 

Medium. .... 17X11 " Double Elephant . . 27X40 " 

Royal . ... 19X24 " Antiquarian . . . 31X53 " 

Super-Royal ... 19x27 " 

The usual method of fastening paper to a drawing board is bv 
means of thumb tacks or small one-ounce copper or iron tacks. 
First fasten the upper left-hand corner and then the lower right, 
pulling the paper taut. The other two corners are then fastened, 
and a sufficient number of tacks placed along the edges to make the 
paper lie smoothly. For very fine work, however, it is better to stretch 
the paper and glue it to the board. Turn up the edges of the paper 
all the way round — the margin being at least one inch — then moisten 
the surface of the paper by means of a sponge or soft cloth, and spread 
paste or glue on the turned-up edges. After removing all the surplus 
water on the paper, press the edges down on the board, commencing 
at one corner and stretching the paper slightly — if stretched too 
much it is liable to split in drying. Place the drawing board in a 
horizontal position until the paper is dry, when it will be found to be 
smooth and tight as a drum head. 
Drawing Board. The drawing board, Fig. 1, is usually made of 
well-seasoned and straight-grained soft pine, the grain running 
lengthwise of the board. Each end of the board is protected by a 



68 



MECHANICAL DRAWING 3 

side strip — If to 2 inches in width — whose edge is made perfectly 
straight for accuracy in using the T-square. Frequently the end 




Fig. 1. Drawing Board 

pieces are fastened by a glued matched joint, nails or screws. Two' 
cleats on the bottom, extending the whole width of the board, will 
reduce the tendency to warp. Drawing boards are made in sizes to 
accommodate the sizes of paper in general use. 

Thumb Tacks. Thumb tacks are used to fasten the paper to 
the drawing board. They are usually made of steel, pressed into 
shape — as in the cheaper grades — or with heads of German silver, the 
points being screwed and riveted to them. For most work, drafts- 
men use small one-ounce copper or iron tacks, as they are cheap and 
can be forced flush with the drawing-paper, thus offering no obstruc- 
tion to the T-square. 

PencilSo Lead pencils are graded according to their hardness, 
the degree of which is indicated by the letter H — as HH, 4H, CH, 
etc. For general use a lead pencil of 5H or 6H should be used, 
although a softer 4H pencil is better for making letters, figures, and 
points. The hard lead pencil should be sharpened as shown in 
Fig. 2 so that in penciling a drawing the lines may be made very fine 
and light. The wood is cut away so that about J or \ inch of lead 



69 



MECHANICAL DRAWING 



projects. The lead can then be sharpened to a chisel edge by rubbing 
it against a bit of sand paper or a fine file, and the corners slightly 
rounded. In drawing the lines the draftsman should place the chisel 
edge against the T-square or triangle, thus 
enabling him to draw a fine line exactly 
through a given point. If the drawing is not 
to be inked, but is made for tracing or for 
rough usage in the shop, a softer pencil, 3H 
or 4H, may be used, so as to make the line£ 
somewhat thicker and heavier. The lead for 
compasses may also be sharpened to a point 
although some draftsmen prefer to use a chisel 
edge for the compasses as well as the pencil. 

In using a very hard lead pencil a light pres- 
sure should be used as otherwise the chisel 
edge will make a deep impression in the paper 
which cannot be erased. 
Erasers. W hat little erasing is necessary in making drawings, 
should be done with a soft rubber. To avoid erasing the surrounding 
work some draftsmen use a card in which a slit is cut about 3 inches 



Fig. 2. Pencil Sharpened 
to a Chisel Point 




Fig. 3. Erasing Shield 











Fig. 4. Metal Erasing Shield 



long and i to J inch wide, Fig. 3. An erasing shield of thin metal, 
Fig. 4, is also very convenient, especially in erasing letters. For 
cleaning drawings when they are completed, a sponge rubber or a 
preparation called "art gum" may be used, but in either case care 
should be taken not to make the lines dull by too hard rubbing. 

T=Square. The T-square, which gets its name from its general 
shape, consists of a thin straight-edge, the blade, with a short piece, 
the head, fastened at right angles to it, Fig. 5. T-squares are usually 
made of wood, the pear and maple woods being used in the cheaper 
^radc-, and the harder woods, like mahogany, with protecting edges 



70 



MECHANICAL DRAWING 5 

of ebony or celluloid, Fig. 6, in the more expensive instruments. 
The head is designed to fit against the edge of the drawing board, 
allowing the blade to extend across the surface of the board. It is 



Fig. 5. Common T-Square 

desirable to have the blade of the T-square make a right angle with 
the head, but this is not absolutely necessary, if the head is always 
placed against the left-hand edge of the board, for the lines drawn 




Fig. 6. Mahogany-Bound T-Square 

with the T-square will then be referred to one edge of the board only, 
and if this edge is straight, the lines will be parallel to each other. 
T-squares are sometimes provided with swiveled heads as it is 
frequently very, convenient to draw lines parallel to each other which 
are not at right angles to 
the left-hand edge of the 
board. To use the T- 
square in drawing parallel 
horizontal lines,* place the 
head of the T-square in 
contact with the left-hand 
edge of the board, Fig.- 7, 
and draw the pencil along 
the upper edge of the 
blade at each new posi- 
tion of the T-square. Only the upper edge should be used as the 

* See page 23. 



p o 

o o I 

|o _o| 



Fig. 7. Drawing Parallel Lines 



71 



6 MECHANICAL DRAWING 

two edges may not be exactly parallel and straight. In trimming 
drawings or cutting the paper from the board, always use the lower 
edge of the T-square so that the upper edge may not be made untrue. 
For accurate work it is absolutely necessary that the upper edge 
of the T-square be exactly straight. To test the straightness of the 

edge two T-squares may be 
placed together as shown in 
Fig. 8. However, a lack of contact 
such as shown in the figure does 
not prove which edge is crooked, 
and for this determination a third 
blade must be used and tried 
with the two given T-squares successively. 

Triangles. Triangles are made of various substances such as 
wood, rubber, celluloid, and steel. Wooden triangles are cheap but 
are likely to warp out of shape; rubber triangles are frequently used, 
and are, in general, satisfactory; celluloid triangles are extensively 
used on account of their transparency, wiiich enables the draftsmen 
to see the work already done even when covered with the triangle. 



Testing the Edge of T-Square 



Fig. 





Fig. 9. 45° and 30°- 60° Triangles 

in using a rubber or celluloid triangle take care that it lies perfectly 
flat and is hung up when not in use; w T hen allowed to lie on the draw- 
ing board with a pencil or an eraser under one corner it will become 
warped in a short time, especially if the room is hot or the sun happens 
ike the triangle. 

Triangles from 6 to S inches on a' side will be found convenient 
Foi most work, although there are many cases where a small triangle 



72 



MECHANICAL DRAWING 7 

measuring about 4 inches on a side will be found useful. Every 
draftsman should have at least two triangles, one having two angles 
of 45 degrees and one right angle; and the other having angles of 
30, 60, and 90 degrees, respectively, Fig. 9. 

The value of the triangle depends upon the accuracy of the 
angles and the straightness of the edges. To test the accuracy of 







t — 


o 

/A 

/ A 


o 


D 

o O 

o o 




o o 







Fig. 10. Testing a Right Angle (45° Triangle) 

the right angle of a triangle, place the triangle with the lower edge 
resting on the T-square in position A, Fig. 10. Now draw the .line 
C D, which, if the triangle be true, will be perpendicular to the edge 
of the T-sq aare. Transfer the triangle to position B, and if the right 
angle of the triangle is exactly 90 degrees the left-hand edge of the 
triangle will exactly coincide with the line C D. 

To test the accuracy of the 45-degree angles place the triangle 
with the lower edge resting on the working edge of the T-square, 





Fig. 11. Testimg 45° Angle (45° Triangle) 

and draw the line E F, Fig. 11. Now without moving the T-square 
place the triangle so that the other 45-degree angle is in the position 
occupied by the first. If the two 45-degree angles coincide they are 
accurate. 



73 



MECHANICAL DRAWING 

Triangles are used in drawing lines at right angles to the T- 

square, Fig. 1 -• and at an angle with the horizontal, Fig. 13. If it is de- 

d to draw a line through the point P, Fig. 14, parallel to a given 



f— 


o 


o 







o 







Fig. 12. Drawing Vertical Parallel Lines 

/; F, two triangles should be used. First, place triangle A with 
ge coinciding with the given hne. Xow take triangle B and 
place one of its edges in contact with the bottom edge of triangle A. 
Holding triangle B firmly with the left hand, slide triangle A to the 
right or to the left until its edge reaches the point P. The line M N 
may then be drawn passing through the point P. In place of the 
triangle B any straight-edge such as a T-square may be used. 





1 3. Drawing Parallel Lines at an Angle with the Horizontal 

A hns may be drawn through a point, perpendicular to a given 
lint I triangles as follows: Let E F, Fig, 15, be the given 

line, and let the point be D. Place the longest side of triangle A so 
that it coincides with the line E F. Place the other triangle (or any 
-t r:i ; _ In the position of the triangle B; then holding B with 

the left hand, place the triangle A in the position C, so that the longest 
Bide passes through the point 1). A line may then be drawn through 
th«- point /' perpendicular to E F- 



74 



MECHANICAL DRAWING 



9 



In previous figures it has been shown how lines may be drawn 
making angles of 30, 45, 60, and 90 degrees with the horizontal. 





Fig. 14. Drawing a Line Parallel to 
Given Line 



Fig. 15. Drawing a Line Perpendicular 
to a Given Line 



It is possible to draw lines forming angles of 15 and 75 degrees by 
placing the triangles as shown in Fig. 16. 



t — 


o 


o 

\ / <^o 


o 

o O 
o 




o o 



Fig. 16. Drawing Angle of 15° and 75 c 



By the use of the triangles and T-square akmost any line may be 
drawn. Suppose it is desired to draw a rectangle having one side 









o 

A 


\ 



\ 




K\ 


\ 


IX 


O 




o 


O 







Fig. 17. Drawing a Rectangle with T-Square and Triangle 

horizontal. First draw by means of the T-square the sides A R 
and DC horizontal and parallel, Fig. 17. Now place one of the 



75 



10 



MECHANICAL DRAWING 



o jX 


o 


mM 




"x^7 




o X V 


o 



Fig. 18. Rectangle Drawn with Triangles 



triangles on the T-square and in positions E and F draw the vertical 
lines DA and B 

If the rectangle is to be 

drawn in some other position 

on the heard, as shown in Fig. 

18, place the 4-Vdegree triangle 

F so that the longest edge is in 

the required direction of the side 

DC. Now, hold the triangle F 

in position and place another 

triangle in position H. By hold- 
ing // in position and sliding triangle F, the sides A B and D C 

may be drawn. To draw the sides A D and B C change triangle 

F to position E and repeat the process. 

Compasses. Compasses are used for 
drawing circles and arcs of circles. The 
cheaper class of instruments are made of 
brass, but they are unsatisfactory on 
account of the odor and the tendency to 
tarnish. The best material is German 
silver, as it does not soil the hands, has 
no odor, and is easy to keep clean. 
Aluminum instruments possess the ad- 
vantage of lightness, but on account of 
the softness of the metal they do not 
wear well. 

The compasses are made in the form 
shown in Fig. 19 and are provided with 
pencil and pen points. Fig. 20 shows 
the compass in position for drawing circles. 
One leg has a socket into which the 
shank of the pencil or pen mounting may 
be inserted. The other leg is fitted with 
a needle point which is placed at the 
center of the circle. Inmost instruments 
the needle point projects through a piece 

of round steel wire with a square shoulder at one or both ends. 
In some instruments the joints are held in position by lock nuts ; 



n passes and 
Attachments 



76 



MECHANICAL DRAWING 



11 



made of thin disks of steel, with notches for using a wrench or forked 
key. Fig. 21 shows the detail of the joint of a high grade instrument. 

Both legs are alike at the joint, 
and two pivoted screws are inserted 
in the yoke. This permits ample 
movement of the legs, yet gives 
the proper stiffness. The flat sur- 
face of one leg is faced with steel, 
the other with German silver, so 
that the rubbing parts may be of 
different metals. Small set screws 
are used to prevent the pivoted 
screws from turning in the yoke. 
The contact surfaces of this joint 
are made circular to exclude dirt 
and to prevent rusting of the 
steel face. 

The details of the socket are 
shown in Fig. 22, Fig. 23, and 
Fig. 24; in some instruments the 
shank and socket are pentagonal, 
Fig. 22, the shank entering the 
Fig. 20. Compasses set for Drawing circles socket loosely, and being held 
in place by means of the screw. Unless used very carefully this 
arrangement is not durable be- 
cause the sharp corners soon wear, 
and the pressure on the set screw 
is not sufficient to hold the shank 
firmly in place. 

In Fig. 23 is shown a round 
shank, the shank having a flat 
top, with a set screw to hold the 
shank in position. A still better 
form of socket is shown in Fig. 24 
the hole being circular and taper- 
ed. The shank fits accurately into the split socket and is clamped by 
a screw on the side; it is held in perfect alignment by a small steel key. 
Both legs of the compass are jointed in order that the lower part 






Details of Compass Joint 



77 



1 2 MECHAN [( !AL DRAWING 

i' the legs may be perpendicular to the paper while drawing circles. 
In this way the needle point makes but a small hole in the paper, 
and both nibs of the pen will press equally on the paper. In penciling 
circles it is not as necessary that the pencil should be kept vertical; 






Pentagonal Shank and Socket Fig. 23. Circular Shank and Socket 

it is a good plan, however, to barn to use them in this way both in 

penciling and inking. The compasses should be held loosely be- 

n the thumb and forefinger. If the needle point is sharp, as it 

a^ should be, only a slight pressure will be 

~ )-, — J nvl required to keep it in place. While 

. i . ( -ireuiar Socket with drawing the circle, incline the compasses 

Set Screw .. . . . . .. . * . 

slightly in the direction or revolution 
and press lightly on the pencil or pen. 

In removing the pencil or pen attachment from the com- 
pass it should be pulled out straight in order to avoid enlarg- 
ing the socket, and thus rendering the instrument inaccurate. 
For drawing large circles use the lengthening bar, Fig. 19, 
Steadying the needle point with one hand and describing 
the circle with the other. 

Dividers. Dividers, which are similar to compasses, are 
\\mi\ to lay off distances on the drawing, either from a scale or 
from other parts of the drawing, Fig. 25. They are also 
used for dividing a line into equal parts. To do this turn 
the dividers in the opposite direction each time, i. c, move 
the point alternately to the right and to the left. The points 
of the dividers should be very sharp so that the holes made 
in the paper will be small, thus assuring accurate spacing. 
Compasses may lie used as dividers by substituting for the 
pencil or pen point an extra steel point, usually furnished 
with the instrument. In place of dividers many drafts- 
men use a needle point. The needle, with the eye-end broken 
Ls fonvd into a handle of soft pine, making a con- 
venient instrument for marking line intersections and 
distal 



78 



MECHANICAL DRAWING 



13 



Bow Pen and Bow Pencil. Ordinary large compasses are too 
heavy and the leverage of the long leg is too great to allow small circles 
to be drawn accurately. For this reason the b6w compasses, Figs. 
26 and 27, should be used on all arcs and circles having a radius of 
less than f inch, such as those which represent boiler tubes and bolt 






Fig. 26. Bow Pencil 



Fig. 27. Bow Pen 



Fig. 28. Bow Divider 



holes. When small circles are drawn, the needle point must be 
adjusted to the same length as the pen or pencil point. If a con- 
siderable change in radius is made, press the points together before 
turning the nut so as to prevent wear in the screw threads. The 
bow dividers, Fig.. 28, replace the ordinary dividers in small work 
and have the advantage of a fixed adjustment. 

Drawing Pen.* For drawing straight lines and curves that are 
not arcs of circles, the line pen — sometimes called the ruling pen — is 




Fig. 29. Drawing Pen 

used, Fig. 29. The distance between the pen points, which regulates 
the width of line to be drawn, is adjusted by the thumb screw, and 
the blades are given a slight curvature so that there will be a cavity 
for ink when the points are close together. 

*See page 22. 



79 



14 MECHANICAL DRAWING 

The pen should not be dipped in the ink but should be filled by 
means of a common steel pen or quill, to a height of about i or § 
inch; if too much ink is placed in the pen it is likely to drop out and 
spoil the drawing. Upon finishing the work wipe the pen with 
chamois or a soft cloth, because most liquid inks corrode the steel. 

In using the pen, care should be taken that both blades bear 
equally on the paper, in order that the line may be smooth. The pen 
is usually inclined slightly in the direction in which the line is drawn 
and should touch the triangle or T-square lightly so as not to press 
the blades together and thereby change the width of the line; the 
pen must not be tipped outward, however, as the danger of blotting 
is greatly increased when the line is drawn so close to the guide. 

Sharpening the Drawing Pen. When it is impossible to make 
a smooth line with the drawing pen, it should be sharpened. Screw 
the blades together and grind them to a parabolic shape by drawing 
the pen back and forth over a small, flat, close-grained oilstone. 
This process, of course, makes the blades dull but insures their being 
of the same length. Now separate the points slightly and rub one 
of them on the oilstone, keeping the pen at an angle of from 10° to 15° 
with the face of the stone, and giving it a slight twisting movement. 
This part of the operation requires great care as the shape of the ends 
must not be altered. After one point has become fairly sharp, grind 
the other in a similar manner, grinding always on the outside of the 
blades and removing the burr from the inside with leather or pine 
wood. Test the pen by filling with ink and drawing several lines. 
Unless the lines are smooth, the grinding must be continued. 

Ink. India ink is always used for drawing as it makes a per- 
manent black line; it is obtainable in solid stick or liquid form. The 
liquid form is much more convenient but contains acid which cor- 
rodes steel and makes it necessary to keep the pen perfectly clean. 

To prepare the ink in stick form for use, put a little water in a 
saucer and place one end of the stick in it; then by a twisting motion 
grind enough ink to make the water black and slightly thickened. 
Now draw a heavy line on a sheet of paper and if after drying the line 
has a grayish appearance, more grinding is necessary. Wipe the 
dry after using to prevent crumbling. It is well to grind the 
ink in small quantities as it does not dissolve readily a second time, 
however, if covered it will keep for two or three days. 



80 



MECHANICAL DRAWING 



15 



Scales. The scales used for obtaining measurements on draw- 
ings are made in several forms, the most convenient being the flat, 
with beveled edges, and the triangular. The scale is usually graduated 
for a distance of 12 inches. The triangular scale, Fig. 30, has six 




Fig. 30. Triangular Scale 

surfaces for different graduations, and the scales are arranged so that 
the drawings may be made in any proportion to the actual size. For 
mechanical work, the common divisions are multiples of two; thus 
drawings are made full size, J size, J, J, T V, ^V> -bt> e ^ c - ^ a drawing 
is J size, 3 inches equals 1 foot, hence 3 inches is divided into 12 equal 
parts and each division represents one inch. If the smallest division 
on a scale represents -jV inch, the scale is said to read to yV inch. 

Scales are often divided into T V> ^, -g^, t Y> e ^ c -> f° r architects 
and civil engineers, and for measuring indicator cards. 

The scale should never be used as a substitute for the triangle or 
T-square in drawing lines. 

Protractor.- The protractor, an instrument used for laying off 
and measuring angles, is made of steel, brass, horn, or paper. When 




Fig. 31. Protractor 



made of metal the central portion is cut out, Fig. 31, so that the drafts- 
man may see the drawing. The outer edge is divided into degrees 



81 



MECHANICAL DRAWING 

and tenths of degrees. To lay off the required angle— use a very 
sharp, hard pencil in order that the measurements may be accurate— 
place the protractor so that the two zero marks are on the given line, 
produced, if necessary, and the center of the circle is at the point 
through which the desired line is to be drawn. 

Irregular Curve. One of the conveniences of a draftsman's 
< outfit is the Frt nch or irregular curve, which is used for drawing curves 
other than arcs of circles, with either pencil or line pen. This instru- 
ment, which is made of wood, hard rubber, or celluloid — celluloid 
being the best — is made in various shapes, one of the most common 
being shown in Fig. 32. Curves drawn with an irregular curve 
are called free hand curves. 

To draw a curve through a series of located points find that 
position of the irregular curve that passes through three points, 




I'i :. 32. Typical Irregular Curva 

a\ . and draw the line through them, Fig. 33. Now shift the curve 
so as to include a part of the curve already drawn and two or three 
more points. Draw the curve through these points, continuing 
this process until the curve is completed. If, at each new setting, 
the line is not carried quite as far as the coincidence of the irregular 
curve would permit, a smoother curve will result. It frequently 
facilitates the work and improves its appearance to draw a pencil 
curve free hand through the points and then use the irregular curve, 
taking care that it always fits at least three points. In inking the 
curve, the blades of the pen must be kept tangent to the curve. 
For certain kin. Is of work, irregular curves of plastic metal are some- 
time^ used to lit exceptionally erratic curves. 

Beam Compasses. The ordinary compasses are suitable for 
drawing circles up to S or 10 inches diameter. For larger circles 

i compasses are provided. The two parts called channels 



82 



MECHANICAL DRAWING 17 

which carry the pen or pencil and the needle point are clamped to a 
wooden beam at a distance equal to the radius of the circle. The 




Fig. 33. Method of Using Irregular Curve 

chumb nut underneath one of the channel pieces makes accurate 
adjustment possible. 

LETTERING 

No mechanical drawing is finished unless all headings, titles, 
and dimensions are lettered in plain, neat type. Many drawings 
are accurate, well-planned, and finely executed but do not present 
a good appearance because the draftsman did not think it worth 
while to letter carefully. Lettering requires time and patience 
especially for the beginner; and many think it a good plan to practice 
lettering before commencing drawing. Poor writing need not neces- 
sarily mean poor lettering, for good writers do not always letter well. 

In making large letters for titles and headings it is often neces- 
sary to use drawing instruments and mechanical aids, but small 
letters, such as those used for dimensions, names of materials, dates, 
etc., should be made free=hand. 

Forming. The student is apt to think that lettering is a form 
of mechanical drawing, that the use of the straight-edge is the prin- 
cipal operation, and that letters, forms, and the spaces between are 
to be figured out by measurement. On the contrary, lettering is 
design, and the draftsman so distributes the letters in the spaces 
arranged for them as to make a combination that will be pleasing 
to the eye. The requirements for a good design are simplicity and 
uniformity. These are acquired by accuracy in detail and by good 
judgment and taste, as no practical rides can be followed which will 



33 



MECHANICAL DRAWING 

invariably produce the same result. Letter forms are, to a certain 

•it. standard The lettering for a title is usually done very care- 
fully and accurately, while practically all of the other lettering on a 
drawing is done rapidly and in a simple style. To develop a letter 
une method of procedure as in drawing a straight line between 
two points. First, draw the guide lines rather carefully and then 
U<>ck out the general form of the letter by a series of short strokes 
of the pencil. Continue this method, straightening the lines and 
rounding the curves of the latter until its form is satisfactory. 

Spacing. The spacing of the letters is very important and is 
best obtained by the unaided eye just as are the proportions of the 
letters. Care must be taken to allow a clear distance between letters, 
the space varying according to the combination. For instance, such 
letters as .!. 1\ and W spread more at one part than at another and 
therefore do not fill the space completely. Of course, when the 
distance between letters is large any such irregularities will not be 
noticeable. The best method for obtaining good space values is by 
sketching in the letters roughly and then bringing them to a good 
appearance by correction and adjustment The first results are, of 
course, unsatisfactory, but after the eye and hand have become 
trained, great improvement will be noticed. A simple aid to this 
development will be found in the use of a piece of cardboard with 
the widths of the enclosing rectangles or parallelograms of the differ- 
ent letters marked on its edge, by which the spacing made by the eye 
may be checked. 

Inking. In practical work most of the lettering is penciled in 

and then finished in ink. As faults in letters which may not be 

noticed in the penciled work stand out clearly after inking, it is not 

advisable to ink in the penciled letter accurately, but rather to im- 

upon it. 

For lettering free-hand, use a pen that will make the full weight 
of line desired without much pressure, holding it squarely on the 
paper and directly in front. A new pen, which is apt to give too fine 
a hue, may be remedied by scratching a little on a rough surface. 
i»t clean and all hardened ink removed so that the nibs 
an- nut spread, the pen will last a long time. A coarser pen must be 
gfa than on smooth paper. 

To remove a fault" line or a blot, let the ink dry thoroughly, 

84 



MECHANICAL DRAWING 



19 



then with a sand rubber, erase the spot carefully, rubbing around it, 
as well. Clean the sand out of the surface with a pencil eraser 
and finally polish down with a piece of ivory or smooth wood. Pencil 
in the parts erased as if doing the work for the first time and again 
ink in, using special care, as the ink is more likely to spread on an 
erased surface than anywhere else. 

Style. There are many styles of letters used by draftsmen, but 
almost any neat letter free from ornamentation is acceptable in 
regular practice. For titles, large Roman capitals are preferred, 
although Gothic and black letters also look well and are much easier 
to make. The vertical and inclined or italicized Gothic capitals 
shown in Fig. 34 and Fig. 35, are neat, plain, and easily made. This 

UPRIGHT GOTHIC 



©aanHHHHi 



QHoranaaH 



Fig. 34. Upright Gothic Capitals 

latter style possesses the advantage over the vertical type in that a 
slight difference in inclination is not apparent. 

The curves of the inclined Gothic letters such as those in B, C, 
G, J, etc., are somewhat difficult to make free-hand, especially if the 
letters are about one-half inch high. In the alphabet, Fig. 36, the 
letters are made almost wholly of slight lines, the corners only 
being curved. 

The first few plates of this work will require no titles, the only 
lettering being the student's name, the date, and the plate number 



85 



20 



MECHANICAL DRAWING 



which will be done in inclined Gothic capitals. Later the subject o* 
lettering will again be taken up in connection with titles and headings 
for drawings which show the details of machines. 

To make the inclined Gothic letters, first draw two parallel lines 
3 D 3- inch apart to mark the height for the letters of the date, name 



A 




KLMNOF>Q/=? 
STUVWXYZ 

Pig. 35. Inclined Gothic Capitals 

and plate number. This is the height to be used on all plates through- 
out this work, unless other directions are given. When two sizes of 
PS are used, the smaller should be about two-thirds as high as 
the larger. The inclination of the letters should be the same for all, 

A BCDETGH/JKLM 

NOP PR S TU VWX YZ 

/2345&7890 

[nclined (lothic Capitals — Straight Lines with Curved Corners 

and as an aid to the beginner, light pencil lines may be drawn 
about 1 inch apart, forming the proper angle with the parallel lines 
already drawn; this angle is usually about 70°, but if a 00° triangle 
Lfl ;' f hand, it may be used in connection with the T-square as shown 

Capital letters such as I), E, F, /„ /, ete., should have their 

and bottom lines coincide with the horizontal guide lines, as other- 

the work will look uneven. Letters, of which 0, G, 0, and O 
be formed of curved or straight lines. If made Cu 



MECHANICAL DRAWING 21 

curved lines, their height should be a little greater than the guide 
lines to prevent their appearing smaller than the other letters. In 
this work they may be made of straight lines with rounded corners 
as such letters are easily constructed and may be made of standard 
height. 

To construct the letter A, use one of the 60° lines as a center line. 
Then from its intersection with the upper horizontal line drop a 
perpendicular to the lower guide line. Draw another line from 
the vertex meeting the lower guide line at the same distance on the 
other side of the center line. The cross line of the A should be a little 
below the center. The V is an inverted A without the cross line. 
For the letter M, the side lines should be parallel and about the same 
distance apart as the guide lines. The side lines of the W are not 
parallel but are farther apart at the top. The J is not quite as wide 
as such letters as II, E, N, R, etc. To make a Y, use the same 
spread as in making a V but let the diverging lines meet the center 
line a little below the middle. 

The lower-case letters are shown in Fig. 37. In such letters 

abcofefgh/jk/mn 
opqrs tuvwxjsz 

Fig. 37. Inclined Gothic Lower-Case Letters 

as m, n, r, etc., make the corners slightly rounding. The letters 
a, b, c, e, g, o, p, q, should be full and rounding. 

The style of the Arabic numerals is given in Fig. 36; Roman 
numerals arc made of straight lines. 

At first the copy should be followed closely and the letters drawn 
in pencil; the inclined guide lines may be used until the proper in- 
clination becomes firmly fixed in mind when they should be aban- 
doned. The horizontal lines, however, are used at all times by 
most draftsmen. After considerable practice has been had the 
letters may be constructed in ink without first using the pencil. 
When proficiency has been attained in the simple inclined Gothic 
capitals, the vertical, block and Roman alphabets should be studied. 

87 






MECHANICAL DRAWING 



HOW TO HOLD DRAWING INSTRUMENTS 

Position of Hand and Instruments. To the student who is 
just starting out with his drawing work, the position in which he 
holds his instruments and the free and easy posture of his hands are 
very important. Just as in playing the piano or in any other process 
where manual dexterity is required, this skill can only be attained by 
practice. The following studies should be used in connection with 



I 



Correct 

Position 



W% 



wmmsmmmm 



^mmmmw^ 



Incorrect Incorrect 

Right Line Pen against T-Square or Triangle 



the instructions given in the forepart of this book and wherever 
references have been given to this section, it is expected that the 
student will study these plates so as to receive helpful suggestions 
in his work. In developing skill in Mechanical Drawing, practice 
is the only method of achieving results after the fundamental princi- 
ple- have been mastered. A very useful collection of "DOXTS" is 
given herewith and these will bear very close study. 




VMldoo 2. Drawing Pencil Line with T-Square and Triangle 



88 



MECHANICAL DRAWING 



23 




Position 3. Inking a Line with Pen and T-Square 




Position 4. Drawing Small Circle with the Compass 



89 






MECHANICAL DRAWING 




Position 5. Drawing Large Circle with Compass with Bent Legs 




Position 6. Dra ■ rck with Spread Compass and Lengthening Bar 



90 



MECHANICAL DRAWING 



25 




Position 7. Adjusting Dividers with One Hand. 

between Legs 



Note Second and Third Fingers 



"DONTS" IN DRAFTING WORK 

Don't fold a drawing. 

Don't stick the dividers into the drawing board. 

Don't use the dividers as picks. 

Don't use the scale to rule lines. 

Don't fail to clean the table, board, and instruments when beginning 

work. 
Don't draw on the lower edge of the T-square. 
Don't cut the sheets of drawing paper with the upper edge of the 

T-square and a knife; use the lower edge. 
Don't put the end of a pencil in the mouth. 
Don't oil the compass joints. 

Don't put away the instruments without cleaning, especially pens. 
Don't use the cheapest materials. 
Don't use the T-square as a hammer. 
Don't screw up the nibs of the pen too tight. 
Don't use a blotter on lines that have been inked. 
Don't run the pen or pencil backward over a line. 
Don't fill a pen over a drawing. 



91 






ME< :hanical drawing 



PRELIMINARY LINE PROBLEMS 

To lav out the paper for the plates of this work, place a sheet 
.1 />' G /'. Fig. 38, od the drawing board 2 or 3 inches from the left- 
hand edge, called the working edge. If placed near the left-hand 
edge, the T-square and triangles can be used with greater firmness 
and the horizontal lines drawn with greater accuracy. In fasten- 
ing the paper on the board, always true it up with the T-square 
according to the long edge of the sheet and use at least 4 thumb tacks 
—one at each corner. If the paper has a tendency to curl, 6 or 8 





A .- 






K : '• 








-a" 










oi •-. 


















I_l 




"T30* 




l 
1 










e 4sN 










1 

l 

1 






D io 


N _ 




VVf) 


Mr 




P_ 


1 
1 

l 




f 










90° 


X 1 


/ 60° 
j. 


90° 
/ 




i 




e e 














9 










O 


- 
















1 


Ml 


1 




p£ 






a 






a G 








H 





































Fig. 38. Standard Lay-Out for Plates 

tacks may be used placing them as shown in Fig. 38; many draftsmen 
prefer one-ounce tacks as they offer less obstruction to the T-square 
and triangles. 

To find the center of the sheet place the T-square so that its 
upper edge coincides with the diagonal corners A and G and with the 
corners /'and Ii, and draw short pencil lines intersecting at C. Now 
with the T-square draw through the point C the dot and dash line 
D /.', and with the T-square and one of the triangles — shown dotted in 

38 draw the dot and dash line II C K. It will probably be 

• to draw CK first and then by means of the T-square or 

triangle, produce (extend) CK to //. In this work always move 



92 



MECHANICAL DRAWING 27 

the pencil from left to right or from the bottom upward; except in 
certain cases. 

After the center lines are drawn measure off 5 inches above 
and below the point C on the line H C K. These points L and M 
may be indicated by a light pencil mark or by a slight puncture by 
means of one of the points of the dividers. Now place the T-square 
against the left-hand edge of the board and draw horizontal pencil 
lines through L and M. 

Measure off 7 inches to the left and right of C on the center 
line D C E and draw pencil lines through these points N and P, 
perpendicular to DE. These lines form a rectangle 10 inches by 
14 inches, in which all the exercises and figures are to be drawn. 
The lettering of the student's name and address, date, and plate 
number are to be placed outside of this rectangle in the J-inch margin. 
In all cases lay out the plates in this manner and keep the center lines 
D E and K H as a basis for the various figures. Ink in the border 
line with a heavy line when the drawing is finished. 

Penciling. In laying out the first few plates of this course the 
work is to be done in pencil and then inked in; later the subject of 
tracing the pencil drawings on tracing cloth and the process of making 
blue prints from these tracings will be taken up. Every beginner 
should practice with his instruments until he understands them 
thoroughly and can use them with accuracy and skill. To aid the 
beginner in this work, the first three plates of this course are practice 
plates; they do not involve any problems and none of the work is 
difficult. The student is strongly advised to draw these plates two 
or three times before making the one to be sent to us for correction. 
Diligent practice is necessary at first; especially on Plate I as it in- 
volves an exercise in lettering. 

Inking. To ink a drawing well requires great care and some 
experience. The student should not attempt to ink in his work until 
he can make a clear-cut, straight line with ease. It is well to practice 
inking in straight pencil lines, rectangles, and triangles in order to 
improve the work on lines, corners, and intersections. These latter 
should be very definite, each line stopping at exactly the right point. 

Before starting to ink in, adjust the pen by means of the thumb 
screw until a good clear line of the desired width is obtained, making 
frequent test lines, on a piece of material similar to that which is to 

93 



28 MECHANICAL DRAWING 

be ,,M d. Keep the pressure of the pen on the paper uniformly light, 
remembering that different weights of lines are not obtained by pres- 
sure as with the ordinary writing pen but only by adjusting the nibs 
of the pen. If the lines arc ragged the pen should be put in order, 
the instructions already given. Sometimes when the 
ink does not flow regularly, moisten the end of the finger and touch the 
point of the pen. Care should be taken not to put too much ink in 
the pen. but on the other hand there must be enough to draw the 
next line as it is difficult to continue a line after re-filling the pen. 
The only way to draw fine lines well is to frequently clean and re-fill 
the pen. [f the amount of ink in the pen is small it is quite likely to 
thicken in the point and cause clogging. When this occurs, draw a 
small strip of paper between the nibs to clean out the clogged ink. 
When drawing, the pen should be held with the thumb screw 
out and should be inclined slightly in the direction in which it is moved. 
Be careful, however, not to incline it too much, as the best of pens 
when incorrectly held will produce poor lines. It is therefore ad- 
visable at the start to acquire the correct method of holding the pen. 
1 )o not press the sides of the pen point too heavily against the ruling 
as this will vary the width of the line; after a little practice the 
pen can be lightly and firmly brought in contact with the paper and 
ruling edge at the same time. The pen should be drawn from left 
to right, the hand being steadied by sliding it on the end of the little 

Always try to get into the easiest position when inking a line, 
even if it becomes necessary to walk around the drawing. The 
average draftsman prefers the standing position while inking as he 
can usually obtain much better results. Keep the ruling edge be- 
tween the line and the body so that the pen will be drawn against the 
ruling edge, for if this is not done, the pen is liable to be pulled off at 
an angle, making a crooked line. He careful after inking a line to 
draw die ruling edge toward the body away from the line in order 
to avoid blotting. Where lines meet at a point, always ink toward; 
die point, being sure to allow one line to dry before inking another. 
Always ink in the top and left-hand lines first, gradually working 
down to the right, thus saving time that otherwise would be lost in 
waiting for the lines t,, dry. When die pen is set at the proper width, 
dniw all the lines of that width before making a change. Never push 

94 



MECHANICAL DRAWING 29 

the pen backward over a line. If a good line is not drawn the first 
time, it is better to go over it again in the same direction, taking 
great care not to widen the original line. 

Ink dries very quickly and should not be left in the pen on account 
of its corrosive effects. The celluloid triangles should be washed 
frequently in water and all ink spots removed. 

In using the compass, bend both legs so that each will be per- 
pendicular to the paper or cloth when the arc or circle is drawn. 
When the pen attachment is used special care must be exercised on 
this point for in no other way can the nibs of the pen be made to bear 
evenly on the surface. In drawing arcs, hold the cylindrical handle 
at the top of the compass loosely between the thumb and the 
forefinger and let it roll between the two during rotation; allow the 
compass to lean slightly in the direction of rotation, pressing down 
the pen point slightly but not the- needle point. Be sure to fix the 
needle point firmly in its proper place on the paper before touching 
the pen to the papei, as otherwise a slip is likely to occur. In 
setting the needle down on any particular center, guide it with a 
finger of the left hand. Avoid making a noticeable hole in the paper. 

Ink in the circumference of a circle with one continuous motion, 
giving an even pressure to the pen throughout the operation and stop- 
ping it sharply at the end of one revolution. Since straight lines can 
be more easily drawn tangent to curves than the reverse, it is always 
advisable to ink in all arcs or circles first. When a number of circles 
are to be drawn from one center, the smaller should be inked first, 
while the center is in the best possible condition. 

PLATE I 

Penciling. To draw Plate I,* take a sheet of drawing paper at 
least 11 inches by 15 inches and fasten it to the drawing board as 
already explained. Find the center of the sheet and draw fine pencil 
lines to represent the lines DE and HK of Fig. 38. Also draw the 
border lines L, M, N, and P. 

Now measure f inch above and below the horizontal center line 
and, with the T-square, draw lines through these points. These 
lines will form the lower lines DC of Fig. 1 and Fig. 2 and the top 
lines AB of Fig. 3 and Fig. 4. Measure f inch to the right and left 

*Note Instructions, pages 22 to 25, inclusive. 

95 






MECHANICAL DRAWING 




96 



MECHANICAL DRAWING 31 

of the vertical center line; and through these points, draw lines parallel 
to the center line. These lines should be drawn by placing the triangle 
on the T-square as shown in Fig. 38. The lines thus drawn, form the 
sides B C of Fig. 1 and Fig. 3 and the sides A D of Fig. 2 and Fig.4. 
Next draw, with the T-square, the line A B A B 4f inches above the 
horizontal center line, and the line D C D C 4f inches below the hori- 
zontal center line. The rectangles of the four figures may now be 
completed by drawing vertical lines 6f inches on each side of the 
vertical center line; these rectangles are each 6 J inches long and 4^ 
inches wide. 

Fig. 1. Exercise with Line Pen and T-square. Divide the line 
A D into divisions each J inch long, making a fine pencil point or 
slight puncture at each division such as E, F, G, H, I, etc. Now 
place the T-square with its head at the left-hand edge of the drawing 
board and through these points draw light pencil lines extending to 
the line B C. In drawing these lines the pencil point must pass 
exactly through the division marks so that the lines will be the same 
distance apart. Start each line in the line A D and do not fall short 
of the line B C or run over it. Accuracy and neatness in penciling 
insure an accurate drawing. Some beginners think that t'hey can 
correct inaccuracies while inking; but experience soon teaches them 
that they cannot do so. 

Fig. 2. Exercise with Line Pen, T-square and Triangle. Divide 
the lower line D C of the rectangle into divisions each J inch long and 
mark the points E, F, G, H, I, J, K, etc., as in Fig. 1. Place the T- 
square about as shown in Fig. 38, and either triangle in position with 
Its 90-degree angle at the left. Now draw fine pencil lines from the 
line D C to the line A B passing through the points E, F, G, H, I, ,7, K, 
etc., keeping the T-square rigid and sliding the triangle toward the right. 

Fig. 3. Exercise with Line Pen T-square and 4.5-degree Tri- 
angle. Lay off the distances A E, B L, etc., each \ inch long on A 
B and B C, respectively. Place the T-square so that the upper edge 
will be below the line D C, and, with the 45-degree triangle, draw the 
diagonal lines through the points laid off. In drawing these lines 
move the pencil away from the body, i. e., from A D to A B and 
from DC to B C. 

Fig. 4. Exercise in Free-Hand Lettering. Draw the center 
line E F, Fig. 39, and light pencil lines Y Z and T X, | inch from the 



97 






MECHANICAL DRAWING 



border lines. With the T-square, draw the line G, i inch from the 
top line and the line H, A inch below 0. The word "LETTERING" 
is t,, be placed between these two lines. Draw the line I, -fs inch below 
//, and -pace the lines included between J and K, -jV inch apart. 

The next style of letters to be discussed is lower-case letters. 
I )raw the line L yV; inch below K and to limit the height of the small 
letters draw a light line \ inch above L. 

Make the space between L and M, ^ inch and draw M and N 
in the same manner as K and L. Now draw C>, ^ inch below r iV, 



G 
H 

1 
J 

K 

L 
M 
N 

P 

R 
S 
U 
V 

V 


f 




T 


/ /-■/ /I 


rR/NE 








THr SUB J 








GFtrA T 








AN/OAI 








fXFCU 








o/sr/G 








F'roflcfpn 








by firiintwH 




A BCD 








a beds 








fP34 








I Jl /// IV 






X 



Pig. 39. Sample Lettering Plate — Fig. 4., Plate I 

P, /, inch below 0, and Q, /* inch below P. Space Q and R as 
A' and /., and draw S, V, V, and IP, /^ inch apart. 

The center line is a great aid in centering the word "LETTER- 
ING" the alphabets, numerals, etc. Indent the words "THE" 
and "Proficimcif* about | inch, as they are the first words of para- 
phs. To draw the guide lines, mark off distances of J inch on 
any line such as J and with the CO-degree triangle draw light pencil 
lines cutting the parallel lines. Sketch the letters in pencil making 
the width of the ordinary letters such as E } F, If, X, R, etc., about 
I their height. Letters like J. .V, and U\ are wider. The space 
between tin- letters depends upon the draftsman's taste, but the be- 
pnner should remember thai letters next to an A or an L should be 
placed Dearer to them than to letters whose sides are parallel: for 



98 



MECHANICAL DRAWING 33 

instance there should be more space between an N and E than be- 
tween an E and H. Similarly a greater space should be left on either 
side of an 1. On account of the space above the lower line of the L, 
a letter following an L should be close to it. If a T follows a T or an 
L follows an L place them near together. In all lettering place the 
letters so that the general effect is pleasing. After the four figures 
are completed, pencil in the lettering for name, address, and date. 
With the T-square draw a pencil line ^ inch above the top border 
line at the right-hand end, and about 3 inches long. At a distance 
of ^ inch above this line draw another line of about the same 
length. These are the guide lines for the word Plate I. Pencil the 
letters free-hand using the 60-degree guide lines if desired. 

Draw in a similar manner the guide lines of the date, name, and 
address in the lower margin, the date of completing the drawing placed 
under Fig. 3, and the name and address at the right, under Fig. 4. 
The street address is unnecessary. It is a good plan to draw lines 
ys inch apart on a separate sheet of paper and pencil the letters in 
order to know just how much space each word will require. The in- 
sertion of the words "Fig. 1," "Fig. 2," etc., is optional with the 
student, but it is advised that he do this extra lettering for the 
practice as well as for convenience in reference. First draw with the 
T-square two parallel lines •£? inch apart under each exercise, the 
lower line being T V inch above the horizontal center line or above the 
lower border line. 

Inking. After all of the penciling of Plate I has been com- 
pleted the exercises should be inked. Before doing this, however, 
see that the pen is in proper condition, and after filling try it on a 
separate piece of paper in order that the proper width of line may be 
drawn. In the first work where no shading is done, use a firm, 
distinct line. The beginner should avoid the extremes; a very light 
line makes the drawing appear weak and indistinct, while a very 
heavy line detracts from its artistic appearance. 

Ink in all the horizontal lines of Fig. 1 first, moving the T-square 
from A to D, and take great care to start and stop the lines exactly 
on the vertical boundary lines. It is necessary to use both triangle 
and T-square for inking A D and B C. In inking Fig. 2 and Fig. 3, 
follow the same directions as for penciling, inking in the vertical and 
oblique lines first and then the border lines. Ink the border lines 

99 



MECHANICAL DRAWING 

of Fig, I first and then the border lines of the plate, making the latter 
heavy and the intersections accurate. The lettering in Fig. 4 
should be done Free-hand, using a steel pen not finer than a Giilott404. 
Now ink in the four figure numbers, plate number, date, and name, 
also free-hand, and then erase the pencil lines. In the finished draw= 
lag there should be no center lines, construction lines, or letters other 
than those in the name, date, etc. 

Cut the -sited 11" X 15", the dash line outside the border line 
of Plate I indicating the edge. 

PLATE II 

Penciling. The horizontal and vertical center lines and the 
border lines for Plate II are laid out in the same manner as were 
those of Plate I. To draw the squares for the six figures, proceed as 
follows: 

Measure off two inches on either side of the vertical center line 
and draw light pencil lines through these points parallel to the vertical 
center line. These lines will form the sides A D and B C of Fig. 2 
and Fig. 5. Parallel to these lines and at a distance of J inch draw 
similar lines to form the sides B C of Fig. 1 and Fig. 4 and A D of 
Fig. 3 and Fig. 6. The vertical sides A D of Fig. 1 and Fig. 4 and 
B ( ' of Fig. 3 and Fig. 6 are formed by drawing lines perpendicular 
to the horizontal center line at a distance of 6 J inches from the center. 

( Complete the figures by laying off lines § inch and 4| inches above 
and below the horizontal center line respectively, thus forming six 
4-inch squares. 

In drawing Fig. 1, divide A D and A B into 4 equal parts, then 
draw horizontal lines through E, F, and G and vertical lines through 
/., .V, and A'. Draw lines from A and B to the intersection of 
lines E and M, and from A and D to the intersection P of lines F and 
/.. Similarly draw D J, J C, C I, and I B. Also connect the points 
0, P, ./, and /, thus forming a square. The four diamond-shaped 
areas are funned by drawing lines from the middle points of A D, 
I />'. BC,and D C to the middle points of lines A P, A 0, B,I B } 
etc., a£ shown in Fig. 1. 

2 is an exercise of straight lines. Divide AD ai.d A B 

int., four equal parts and draw horizontal and vertical lines as in 

I. Now divide these dimensions, A L, M X, etc., and E F 3 

100 



MECHANICAL DRAWING 



35 




101 



MECHANICAL DRAWING 

. into four equal parts— each J inch— and draw light pencil 
Lines with the T-square and triangle as shown. 

In Fig. 3, divided I) and A B into eight equal parts, and through 
the points 0, P, Q, H, I f J, etc., draw horizontal and vertical lines. 
Now draw lines connecting and II, P and J, Q and J, etc. As 
these lines form an angle of 45 degrees with the horizontal, a 45- 

nee triangle may be used. Similarly from each one of the given 
point- on A B and .1 D> draw lines at an angle of 45 degrees to B C 
and D C respectively. 

1 is drawn with the compasses. Draw the diagonals A C 
and D B, and with the T-square draw the line EH. Now mark 
off on E II distances of \ inch, and with if as a center describe, by 
means of the compasses, circles having radii respectively 2 inches. 
1 J inches, 1 inch, § inch, \ inch, and J inch. Similarly with JjTasa 
center and a radius of lj inches and lj inches respectively draw the 
ans FG and I J and K L and 31 X, being careful to end the arcs 
in the diagonal-. 

5 is an exercise with the line pen and compasses. Draw 
the diagonals -1 C and D B, the horizontal line L 31 and the vertical 
line E F passing through the center Q. Mark off distances of J inch 
on /. M and E F and complete the squares N R R' N', etc. With 
the bow pencil adjusted so that the distance between the pencil point 
and the needle point is J inch, draw arcs having centers at the corners 
of the inner squares. The arc whose center is N will be tangent to 
the lines A L and .1 E and the arc whose center is will be tangent 

\ N' and N R. Since the smallest square has 1 inch sides, 
the l-inch ares drawn with Q as a center will form a circle. 

In Fig. ('», draw the center lines E F and L 31, and find the cen- 
ters <>f the tour squares thus formed. Through the center / draw the 
construction lines // / T and RIP forming angles of 30 degrees 
with /. P. Now adjust the compasses to draw circles having a radius 
of "He inch, and with / as a center, draw the circle H P T R. With 
the Same radius draw the arcs with centers at A, />, (\ and D, and 

draw the semicircles with centers at L, I\ M, and E. Now draw 
the arcs as shown having centers at the centers of the four squares. 
To locate the centers of the six small circles within the circle // P T R 
<iraw a circle with a radius of -] J inch and having the center in I. 
The small circles each have a radi'is of T \ inch. 



102 



MECHANICAL DRAWING 37 

Inking. In Plate II ink in only the lines shown full in the speci- 
men plate. First ink the star and then the square and diamonds. 
As this is an exercise for practice, the cross-hatching should be done 
without measuring the distance between the lines and without the 
aid cf any cross-hatching device. The lines should be about T V inch 
apart. After inking in the plate all construction lines should be 
erased. 

In inking Fig. 2 first ink the principal horizontal and vertical 
lines and then very carefully ink in the short lines. Make these lines 
all of the same width. 

• Fig. 3 is drawn entirely with the 45-degree triangle. In inking 
the oblique lines make P I, R K, T M, etc., of the usual width, while 
the alternate lines II, Q J, S L, etc., should be somewhat heavier. 
All of the lines which slope in the opposite direction are light. Now 
ink m the border lines and erase all other horizontal and vertical lines. 

In inking Fig. 4 use only the compasses, adjusting the legs so 
that the pen will always be perpendicular to the paper. In inking 
the arcs, see that the pen stops exactly at the diagonals. The inner 
circle and the next but one should be dotted as shown in the specimen 
plate. After inking the circles and arcs erase the construction lines 
that are without the outer circles, leaving in pencil the diagonals inside 
the circles. 

In Fig. 5 draw all arcs first and then the straight lines meeting 
these arcs, as it is much easier to make a straight line meet an arc 
or tangent to it, than the reverse. Leave all construction lines in 
pencil. This exercise is difficult, and as in all mechanical and ma- 
chine drawing, arcs and tangents are frequently used, the beginner is 
advised to draw this exercise several times. 

Fig. 6 is an exercise with compasses. If the laying out has been 
accurately done in pencil, the inked arcs will be tangent to each other 
and the finished exercise will have a good appearance. If, however, 
the distances were not accurately measured and the lines carefully 
drawn, the inked arcs will not be tangent. The arcs whose centers 
are L, F, M, and E, and A, B y C, and D should be heavier than the 
rest. The small circles may be drawn with the bow pen. After 
inking the arcs all construction lines should be erased. 

Finally ink in the figure numbers, the border lines of the plate, 
name, address, and plate number as in Plate L ' 

103 



38 MECHANICAL DRAWING 

PLATE III 

Penciling. Plate III should be laid out in the same manner 
as Plate II, that is, for size and border lines. In laying out the 
sixteen rectangles, however, the space between the center lines and 
rectangles must in every case be made \ inch. Each rectangle is 
to be filled in with what is called section lining, illustrating the 
material of which the object is composed, and, therefore, differing 
accordingly. The conventions here shown are standard, and some 
of them will be used by the student in later work in Machine 
I hrawing. Familiarity with them is of value to any draftsman. In 
drawing section lines of this character, the closeness of the lines 
should be governed by the area being sectioned. For large areas 
use a rather wide spacing; for small areas use a narrow spacing. 
In showing a section of any machine, the different parts are dis- 
tinguished by altering the slope of the section lines, whether of the 
same material or not. 

Draw the sixteen figures in full and then draw the border lines 
of the plate. Make the lettering conform to that in Plate I and 
Plate II. 

Inking. After all the penciling of Plate III has been completed, 
the exercise should be inked, including the titles. 



104 



MECHANICAL DRAWING 



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MECHANICAL DRAWING 

PART II 



In Part I the instructions and the problems worked out have 
been designed to teach the student the elementary operations of 
Mechanical Drawing, giving him a knowledge of the instruments, 
an ability to draw a straight and true line, and to make up simple 
figures. A fair degree of drawing ability is now assumed and we 
can pass on to more complicated problems. Wherever we turn 
for subjects, however, we find a knowledge of geometrical figures 
and their properties is absolutely essential to a clear understanding 
of the problems chosen and we will therefore turn to a discussion 
of these geometrical figures and the problems which involve them. 

GEOMETRICAL DEFINITIONS 

A point is used for marking position; it has neither length, 
breadth, nor thickness. 

LINES 

A line has length only; it is produced by the motion of a point. 

A straight line or right line is one that has the same direction 
throughout. It is the shortest distance between two points. 

A curved line is one that is constantly changing in direction. 
It is sometimes called a curve. 

A broken line is one made up of several straight lines. 

Parallel lines are lines which lie in the same plane and are equally 
distant from each other at all points. 

A horizontal line is one having the direction of a line drawn 
upon the surface of water that is at rest. It is a line parallel to the 
horizon. 

A vertical line is one that lies in the direction of a thread sus- 
pended from its upper end and having a weight at the lower end. 
It is a line that is perpendicular to a horizontal plane. 

An oblique line is one that is neither vertical nor horizontal. 



107 



MECHANICAL DRAWING 

In Mechanical Drawing, lines drawn along the edge of the 
en the head of the T-square is resting against the left- 
hand • the lu.ard, are called horizontal lines. Those drawn 
at right angles or perpendicular to the edge of the T-square are 
called vertical lines. 

If two lines cut each other, they are called intersecting lines, 
and the point at which they cross is called the point of intersection. 

ANGLES 

An angle is the measure of the difference in direction of two 
lines. The lines are called sides, and the point of meeting, the 



Right Angle Fig. 41. Acute Angle Tig. 42. Obtuse Angle 

vertex. The size of an angle is independent of the length of the lines. 

If one straight line meets another (extended if necessary), 

40, so that the two angles thus formed are equal, the lines are 
I to be perpendicular to each other and the angles formed are 
called right angles. 

An acute angle is less than a right angle, Fig. 41. 

An obtuse angle is greater than a right angle, Fig. 42. 

SURFACES 

A m rface is produced by the motion of a line; it has two dimen- 

length and breadth. 
A plane figure is a plane bounded on all sides by lines; the 
e included within these lines (if they are straight lines) is called 
a polygon or a rectilinear figure. 

POLYGONS 

A polygon is a plane figure bounded by straight lines. The 
boundary lines arc called the sides and the sum of the sides is called 
the }>< rimeii r. 

Pol; gons arc classified according to the number of side-. 

A triangle is a polygon of three sides. 



108 



MECHANICAL DRAWING 



43 



A quadrilateral is a polygon of four sides. 
A pentagon is a polygon of five sides, Fig. 43. 
A hexagon is a polygon of six sides, Fig. 44. 
A heptagon is a polygon of seven sides. 
An octagon is a polygon of eigr/jtf sides, Fig. 45. 




Fig. 43. Pentagon 



Pig. 44. Hexagon 



Fig. 45. Octagon 



A decagon is a polygon of ten sides. 

A dodecagon is a polygon of twelve sides. 

An equilateral polygon is one all of whose sides are equal. 

An equiangidar polygon is one all of whose angles are equal. 

A regular polygon is one all of whose angles and all of whose 
sides are equal. 

Triangles. A triangle is a polygon enclosed by three straight 
lines called sides. The angles of a triangle are the angles formed by 
the sides. 

A right-angled triangle, often called a rigid triangle, Fig. 46, 
is one that has a right angle. The longest side (the one opposite 





Fig. 46. Right- 
Angled Triangle 



Fig. 47. Acute Angled 
Triangle 




Fig. 48. Obtuse-Angled 
Triangle 



the right angle) is called the hypotenuse, and the other sides are 
sometimes called legs. 

An acute-angled triangle is one that has all of its angles acute, 
Fig. 47. 

An obtuse-angled triangle is one that has an obtuse angle, Fig. 48. 

An equilateral triangle is one having all of its sides equal, Fig. 49. 

An equiangidar triangle is one having all of its angles equal. 



109 



MECHANICAL DRAWING 

triangle.. Fig. 50, is one, two of whose sides are equal. 
_\ - - _ 51, is one, no two of whose sides are equal. 






: ;uilateral ?elea "1. Scalene Triangle 

Triangle Triangle 

The base of a triangle is the lowest side; it is the side upon which 

the triangle is supposed to stand. Any side may, however, be taken 

In an isosceles triangle, the side which is not one of 

equal sides is usually considered as the base. 

The altitude of a triangle is the perpendicular drawn from the 
vertex to the base. 

Quadrilaterals. A quadrilateral is a polygon bounded by four 
straight lines, as Fig. 52 

The diagonal of a quadrilateral is a straight line joining two 
oppo>ite vertices. 

Trapezium. A trapezium is a quadrilateral, no two of whose 
are parallel. 

Trapezoid. A trapezoid is a quadrilateral having two -ides 




Fig. 52. Quadri:.. 33. Trapezoid 54. Parallelogram 

parallel, The parallel sides are called the bases and the 

perpendicular distance between the bases is called the altitude. 

Paralhlngram. A parallelogram is a quadrilateral whose 
re parallel. Fig. 54. 

lour kinds of parallelograms: rectangle, square, 
rhoo I rhomboid. 

• i - a parallelogram whose angles are right 

parallelogram all of whose sides are 
J and wl re right angl- 



110 



MECHANICAL DRAWING 



45 



The rhombus, Fig. 57, is a parallelogram whose sides are equal 
but whose angles are not right angles. 




Fig. 55. Rectangle 



Fig. 56. Square 



Fig. 57. Rhombus 



The rhomboid is a parallelogram whose adjacent sides are 
unequal, and whose angles are not right angles. 

CIRCLES 

A circle is a plane figure bounded by a curved line called the 
circumference, every point of which is equally distant from a point 
within called the center, Fig. 58. 

A diameter of a circle is a straight line drawn through the center, 
terminating at both ends in the circumference, Fig. 59. 

A radius of a circle is a straight line joining the center with the 






Fig. 58. Circle 



Fig. 59. Diameter, 
Radius, Tangent 



Fig. 60. Quadrant 



circumference. All radii of the same circle are equal and their length 
is always one-half that of the diameter. 

An arc is any part of the circumference of a circle. An arc 
equal to one-half the circumference is called a semi-circumference, 
and an arc equal to one-quarter of the circumference is called a 
quadrant, Fig. 60. A quadrant may mean the arc or angle. 

A chord, Fig. 61, is a straight line which joins the extremities 
of an arc but does not pass through the center of the circle. 

A secant is a straight line which intersects the circumference 
in two points, Fig. 61. 

A segment of a circle, Fig. 62, is the area included between an 
arc and a chord. 



111 






MECHANICAL DRAWING 



is the area included between an arc and two radii drawn 
to the extremities of the arc, Fig. 62. 

A tangent is a straight line which touches the circumference at 
only one point, called the point oftangency or contact, Fig. 59. 





Chord and 
- tut 



Fig. 62. Segment 
and Sector 




Fig. 63. Concentric 
Circles 



Concentric circles are circles having the same center, Fig. 63. 

An inscribed angle is an angle whose vertex lies in the circum- 
ference and whose sides are chords. It is measured by one-half 
the intercepted arc, Fig. 64. 

A central angle is an angle whose vertex is at the center of the 
circle and whose sides are radii, Fig. 65. 





>. Inscribed 
Angle 



Fig. 65. Central 
Angle 




An in. scribed polygon is one whose vertices lie in the eircum- 
ference and whose sides are chords, Fig. 66. 

MEASUREMENT OF ANGLES 

T<> measure an angle, take any convenient radius and describe 
;m arc with the center at the vertex of the angle. The portion of 
the arc included between the sides of the angle is the measure of the 
angle. If the arc has a constant radius, the greater the divergence 
■•I the sides, the longer will be the arc. If there are several arcs 
drawn with the same center, the intercepted arcs will have different 
ths but they will all be the same fraction of the entire circum- 

ce. 



112 



MECHANICAL DRAWING 



47 



In order that the size of an angle or arc may be stated with- 
out saying that it is a certain fraction of a circumference, the cir- 
cumference is divided into 360 
equal parts called degrees, Fig. 
67. Thus, it may be said that 
a certain angle contains 45 de- 
grees, i.e., it is 3%% = i of a 
circumference. In order to ob- 
tain accurate measurements 
each degree is divided into 60 
equal parts called minutes and 
each minute into 60 equal parts 

Called Seconds. Fig. 67. Angular Measurement 




SOLIDS 

A solid has three dimensions — length, breadth, and thickness. 
The most common forms of solids are 'polyhedrons, cylinders, cones, 
and spheres. 

POLYHEDRONS 

A polyhedron is a solid bounded by planes. The bounding planes 
are called faces and their intersections are called edges. The inter- 
sections of the edges are called vertices. 

A polyhedron having four faces is called a tetrahedron; one having 
six faces, a hexahedron; one having eight faces, and octahedron, Fig. 68; 
one having twelve faces, a dodecahedron, etc. 

Prisms. A prism is a polyhedron having two opposite faces, 
called bases, which are equal and parallel, and other faces, called 





< 



>. 



Fig. G8. Octahedron 



Fig. 69. Prism 



Fig. 70. Right Prism 



lateral faces, which are parallelograms, Fig. 69. The altitude of a 
prism is the perpendicular distance between the bases. The area 
of the lateral faces is called the lateral area. 



113 






MECHANICAL DRAWING 



Prisms are called triangular, rectangular, hexagonal, etc., accord- 
to the shape of the bases. Further classifications are as follows: 




^/\ 


yr 


1 

1 
1 
1 










. 1. Parallelopiped 



Fig. 72. Rectangular Paral- 
lelopiped 



Fig. 73. Truncated 
Prism 



A right prism is one whose lateral faces are perpendicular to 
the bases, Fig. 70. 

A regular prism is a right prism having regular polygons for 
bases. 

Parallelopiped. A parallelopiped is a prism whose bases are 
parallelograms. Fig. 71. If all the edges are perpendicular to the 
bases, it is called a right parallelopiped. 

A rectangular parallelopiped is a right parallelopiped whose 
bases and lateral faces are rectangles, Fig. 72. 

A cube is a rectangular parallelopiped all of whose faces are 
>quares. 

A truncated prism is the portion of a prism included between 
the base and a plane not parallel to the base, Fig. 73. 

Pyramids. A pyramid is a polyhedron whose base is a polygon 
and whose lateral faces are triangles having a common vertex called 
the vertex of the pyramid. 






; . Pyramid 



Fig. 75. Regular Pyramid 



Fig. 76. Frustum of 
Pyramid 



The altitude of the pyramid is the perpendicular distance from 
the vertex to the base. 

Pyramids are named according to the kind of polygon forming 
the base, viz, triangular, quadriaugular, Fig. 7 '4. pentagonal, Fig. 75, 
hexagonal. 



114 



MECHANICAL DRAWING 



49 



A regular pyramid is one whose base is a regular polygon and 
whose vertex lies in a perpendicular erected at the center of the base, 
Fig. 75. 

A truncated pyramid is the portion of a pyramid included 
between the base and a plane not parallel to the base. 

A frustum of a pyramid is the solid included between the base 
and a plane parallel to the base, Fig. 76; its altitude is the perpendic- 
ular distance between the bases. 

CYLINDERS 

A cylinder is a solid having as bases two equal parallel surfaces 
bounded by curved lines, and as its lateral face the continuous 




Fig. 77. Cylinder 





Fig. 79. Inscribed Cylinder 



surface generated by a straight line connecting the bases and moving 
along their circumferences. The bases are usually circles and such 
a cylinder is called a circular cylinder. Fig. 77. 

A right cylinder, Fig. 78, is one whose side is perpendicular to 
the bases. 

The altitude of a cylinder is the perpendicular distance between 
the bases. 

A prism whose base is a regular polygon may be inscribed in 
or circumscribed about a circular cylinder, Fig. 79. 

CONES 

A cone is a solid bounded by a conical surface and a plane which 
cuts the conical surface. It may be considered as a pyramid with 
an infinite number of sides, Fig. 80. 

The conical surface is called the lateral area and it tapers to a 
point called the vertex; the plane is called the base. 

The altitude of a cone is the perpendicular distance from the 
vertex to the base. 



115 






MECHANICAL DRAWING 



is any straight line from the vertex to the 
circumference of the base. 

A circular com is a con*.' whose base is a circle. 

A riij/it circular cone, or cone of revolution, Fig. 81, is a cone 















Right Circular 
Cone 



Fig. ^2. Frustum of 
Cone 



whose axis is perpendicular to the base. It may be generated by 
the revolution of a right triangle about one of the legs as an axis. 
A frustum of a cone, Fig. 82, is the portion of the cone included 
bet wren the base and a plane parallel to the base; its altitude is the 
perpendicular distance between the bases. 

SPHERES 

A spht re is a solid bounded by a curved surface, every point 
of which is equally distant from a point within called the center. 

The diameter is a straight line drawn through the center and 
having its extremities in the curved surface. The radius — J diameter 
- is the straight line from the center to a point on the surface. 

A plane is tangent to a sphere when it touches the sphere in only 







Fig. S4. Great and Small Circle 



one point. A plane perpendicular to a radius at its outer extremity 
is tangent t<> the sphere, Fig. 83. 

An inscribed polyhedron is a polyhedron whose vertices lie in the 
BUrface of the sphere. 

A circumscribed polyhedron is a polyhedron whose faces are 
enl t<» a sphere, 



116 



MECHANICAL DRAWING 



51 



A great circle is the intersection of the spherical surface and 
a plane passing through the center of the sphere, Fig. 84. 





Fig. 85. Intersections of Plane with Cone and Cylinder Giving Ellipses as Shown in (b) and (d) 

A small circle is the intersection of the spherical surface and 
a plane which does not pass through the center, Fig. 84. 

CONIC SECTIONS 

If a plane intersects a cone at various angles with the base the 
geometrical figures thus formed are called conic sections. A plane 
perpendicular to the base passing through the vertex of a right 
circular cone forms an isosceles triangle. If the plane is parallel 
to the base, the intersection of the plane and the conical surfaces 
will be the circumference of a circle. 

Ellipse. If a plane AB, Fig. 85a, 
cuts a cone oblique to the axis of the 
cone, but not cutting the base, the curve 
formed is called an ellipse, as shown in 
Fig. 85b, this view being taken per- 
pendicular to the plane AB. If the 
plane cuts a cylinder as shown in Fig. 
85c, the ellipse shown in Fig. 85d is 
the result, this view being also taken perpendicular to the plane 
AB, An ellipse may be defined as a curve generated by a 'point 




Fig. 



Diagram Showing Constants 
of Ellipse 



117 






MECHANICAL DRAWING 




Intersection of Plane with Cone 
Parallel t<. Element of Cone and Para- 
bolic Section Produced 







Diagram Showing Constants of 
Parabola 




Intersection of Plane with Cone, 
Paralli-l t.> Asia and Hyperbolic Section 
Produced 




m Showing Con- 



moving in a plane in such a man- 
ner that the sum of the distances 
from the point to two fixed points 
shall always be constant. 

The two fixed points are 

called foci, Fig. 86, and shall lie 

on the longest line that can be 

drawn in the ellipse which is 

called the major axis; the shortest 

line is called the minor axis; and 

is perpendicular to the major axis 

at its middle point, called the center. 

An ellipse may be constructed 

if the major and minor axes are 

given or if the foci and one axis are 

known. 

Parabola. If a plane AB, Fig. 
87a, cuts a cone parallel to an ele- 
ment of the cone, the curve resulting 
from this intersection is called a 
parabola, as shown in Fig. 87b, 
the view being taken perpen- 
dicular to the plane AB. This 
curve is not a closed curve for the 
branches approach parallelism. 
A parabola may be defined 
as a curve every point of which 
is equally distant from a line and 
a point. 

The point is called the focus, Fig. 88, 
and the given line, the directrix. The 
line perpendicular to the directrix and 
passing through the focus is the axis. 
The intersection of the axis and the curve 
is the vertex, 

Hyperbola. If a plane AB, Fig. 89a, 
cuts a cone parallel to its axis, the 
resulting curve is called a hyperbola, 



118 



MECHANICAL DRAWING 53 

Fig. 89b, the view being taken perpendicular to the plane AB. 

Like the parabola, the curve is not closed, the branches con- 
stantly diverging. 

A hyperbola is defined as a plane curve such that the difference 
between the distances from any point in the curve to two fixed points 
is equal to a given distance. 

The two fixed points are the foci and the line passing through 
them is the transverse axis, Fig. 90. 

Rectangular Hyperbola. The form of hyperbola most used 
in Mechanical Engineering is called the rectangular hyperbola 
because it is drawn with reference to rectangular coordinates. This 
curve is constructed as fol- 
lows: In Fig. 91, OX and 
OY are the two coordinate 
axes drawn at right angles 
to each other. These lines 
are also called asymptotes. 
Assume A to be a known 
point on the curve. Draw 
AC parallel to OX a n d 

AD perpendicular tO OX. Fig- 91# Construction of Rectangular Hyperbola 

Mark off any convenient 

points on AC such as E, F, G, and II, and through these points 
draw EE', FF' ', GG' , and HH f , perpendicular to OX. Connect 
E, F, G, H, and C with 0. Through the points of intersection of 
the oblique Ikies and the vertical line AD' draw the horizontal 
lines LL', MM' ', NN f , PP f , and QQ'\ The first point on the curve 
is the assumed point A, the second point is R, the intersection of 
LL f and EE' , the third the intersection S, and so on. 

In this curve the products of the coordinates of all points are 
equal. Thus LRxPiE' = MSxSF' = NTx TG'. 

ODONTOIDAL CURVES 

Cycloidal Curves. Cycloid. The cycloid is a curve generated 
by a point on the circumference of a circle which rolls on a straight 
line tangent to the circle, as shown at the left, Fig. 92. 

The rolling circle is called the describing or generating circle, 
the point on the circle, the describing or generating point, and the 



119 




MECHANICAL DRAWING 



_ hich the circle rolls, the director. In order that the 
curve described by the point may be a true cycloid the circle must 
roll witho -lipping. 

In case the generating circle rolls upon the inside 
i r circle, the curve thus generated is a hypocycloid, 

JJ05P* 








TrU^GBJ^T OR DIRECTOR 

■ imetrical Constructions for Cycloid and Hypocycloid 

If the generating circle has a diameter equal to the radius 
of the director circle the hypocycloid becomes a straight line. 

■i/cloid. If the generating circle rolls upon the outside 

of the director circle, the curve generated is an epicycloid, Fig. 93. 

Involute Curves. If a thread of fine wire is wound around a 

cylinder or eirele and then unwound, the end will describe an involute 

curve. The involute may be defined as a curve generated by a point 

■<t wiling on a circle, known as the base circle, Fig. 94. 



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rical Construction 
Epicycloid 



Fig. 94. Geometrical Constn. 
for an Involute 



The details of the ellipse, parabola, hyperbola, cycloid, and 
involute will be taken up in connection with the plates. 

The most important application of the cycloidal and involute 
curve- is in the cutting of all forms of gear teeth. It has been found 
that the teeth of gears when cut accurately to either of these curves 
will mesh with the least friction and run with exceptional smooth- 
The development of these gears and of the machines for 






cutting tlirin has reached a high state of perfection. 



120 



MECHANICAL DRAWING 55 

GEOMETRICAL PROBLEMS 

The problems given in Plates IV to VIII inclusive have been 
cnoscn because of their particular bearing* on the work of the 
mechanical draftsman. They should be solved with great care, as the 
principles involved will be used in later work. 

PLATE IV 

Penciling. The horizontal and vertical center lines and the 
border lines should be laid out in the same manner as in Plate I. 
Now measure off 2\ inches on both sides of the vertical center line 
and through these poinis draw vertical lines as shown by the dot 
and dash lines, Plate IV. In locating the figures, place them a little 
above the center so that there will be room for the number of the 
problem. 

Draw in lightly the lines of each figure with pencil and after the 
entire plate is completed, ink them. In penciling, all intersections 
must be formed with great care as the accuracy of the results depends 
upon it. Keep the pencil points in good order at all times and draw 
lines exactly through intersections. 

Problem 1. To bisect a given straight line. 

Draw the horizontal straight line A C about 3 inches long. 
With the extremity A as a center and any convenient radius — 
about 2 inches — describe arcs above and below the line A C. 
With the other extremity C as a center and with the same radius 
draw similar arcs intersecting the first arcs at D and E. The radius 
of these arcs must be greater than one-half the length of the line in 
order that they may intersect. Now draw the straight line D E 
passing through the intersections D and E. This line will cut A C 
at its middle point F. 
Therefore 

AF = FC 

Proof. Since the points D and E are equally distant from A 
and C a straight line drawn through them is perpendicular to A C 
at its middle point F. 

Problem 2. To construct an angle equal to a given angle. 

Draw the line C about 2 inches long; and the line A of 
about the same length. The angle formed by these lines may ba 

121 






MECHANICAL DRAWING 



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122 



MECHANICAL DRAWING 57 

any convenient size — about 45 degrees is suitable. This angle 
A C is the given angle. 

Now draw F G, a horizontal line about 2} inches long, and let 
F, the left-hand extremity, be the vertex of the angle to be con- 
structed 

With as a center and any convenient radius — about 1 J inches 
— describe the arc L M cutting both A and C. With F as a 
center and the same radius draw the indefinite arc Q. Now set 
the compass so that the distance between the pencil and the needle 
point is equal to the chord L M. With Q as a center and a radius 
equal to L M draw an arc cutting the arc Q at P. Through 
F and P draw the straight line F E. The angle E F G is the re- 
quired angle since it is equal to A C. 

Proof. Since the chords of the arcs L M and P Q are equal, 
the arcs are equal. The angles are equal because with equal radii 
equal arcs are intercepted by equal angles. 

Problems 3 and 4. To draw through a given point a line parallel 
to a given line. 

First Method. Draw the straight line A C about 3J inches 
long and assume the point P about 1 J inches above A C. Through 
the point P draw an oblique line F E forming any convenient angle 
— about 60 degrees — with A C. Now construct an angle equal to 
P F C having its vertex at P and the line E P as one side. (See 
Problem 2.) The straight line P forming the other side of the 
angle E P will be parallel to A C. 

Proof. If two straight lines are cut by a third making the 
corresponding angles equal, the lines are parallel. 

Second Method. Draw the straight line A C about 3f inches 
long and assume the point P about 1} inches above A C. With 
P as a center and any convenient radius — about 2| inches — draw 
the indefinite arc E D cutting the line A C. Now with the same 
radius and with D as a center, draw an arc P Q. Set the com- 
pass so that the distance between the needle point and the pencil 
is equal to the chord P Q. With D as a center and a radius equal 
to P Q, describe an arc cutting the arc E D at H. A line drawn 
through P and H will be parallel to A C. 

Proof. Draw the line Q H. Since the arcs P Q and H D 
are equal and have the same radii, the angles P H Q and H Q D 



123 



MECHANICAL DRAWING 

.,,-,. equal. Two lines are parallel if the alternate interior angles 

qual. 

Problems 5 and 6. To draw a perpendicular to a line from 

a point in the hue. 

First Method. WHEN THE POINT IS NEAR THE MIDDLE OF 

THE LINE. 

1 )i ';iw the line A C about 3} inches long and assume the point 
P near the middle of the line. With P as a center and any convenient 
radius— about \\ inches — draw two arcs cutting the line AC at 
E and F. Now with E and F as centers and any convenient radius 
about 2] inches — describe arcs intersecting at 0. The line OP 
will be perpendicular to A C at P. 

Proof. The points P and are both equally distant from E 
and F. Hence a line drawn through them is perpendicular to 
E F at P. 

vnd Method. WHEN THE POINT IS NEAR THE END OF 
THE LINE. 

Draw the line A C about 3 J inches long. Assume the given 
point P to be about § inch from the end A. With any point D 
as a center and a radius equal to DP, describe an arc cutting A C 
at E. Through E and D draw the diameter £0. A line from 
to P is perpendicular to ^4 C at P. 

Proof. The angle OPE is inscribed in a semicircle; hence 
ii is a right angle, and the sides OP and PE are perpendicular 
to each other. 

Lettering. After completing these figures draw pencil lines for 
tlif lettering. Place the words "Plate IV" and the date and the 
name in the border, as in preceding plates. To letter the words 
'Problem 1," "Problem 2," etc., draw 7 three horizontal lines f inch, 
j inch, and t \ inch, respectively, above the horizontal center line 
and the lower border line to serve as a guide for the size of the letters. 

Inking. In inking Plate IV, ink in the figures first. Make the 
line J (\ Problem 1, a full line as it is the given line; make the arcs 
and the line J) F doitvd as they are construction lines. Similarly in 
Problem 2, make the sides of the angles full lines and the chord 
/. M and the arcs dotted. Follow the same plan in inking the lines 
of Problems 3, A, •", and 6. In Problem 6, ink in only that part of 
the circumference which passes through the points 0, P, and E. 



124 



MECHANICAL DRAWING 59 

After inking the figures, ink in the heavy border line, and the 
lettering. 

PLATE V 

Penciling. In laying out the border , lines and center lines 
follow the directions given for Plate IV. Draw the dot and dash 
lines in the same manner, as there arc to be six problems on this plate. 

Problem 7. To draw a perpendicular to a line from a point 
without the line. 

Draw the straight line A C about 3J inches long, and assume 
the point P about lj inches above the line. With P as a center and 
any convenient radius — about 2 inches — describe an arc cutting A C 
at E and F. The radius of this arc must always be such that it will 
cut A C in two points; the nearer the points E and F are to A and C, 
the greater will be the accuracy of the work. 

Now with E and F as centers and any convenient radius — about 
2 J inches — draw the arcs intersecting below A at T. A line 
through the points P and T will be perpendicular to A C. In case 
there is not room below A C to draw the arcs, they may be drawn 
intersecting above the line as shown at N. Whenever convenient 
draw the arcs below A C for greater accuracy. 

Proof. Since P and T are both equally distant from E and F, 
the line P T is perpendicular to A C. 

Problems 8 and 9. To bisect a given angle. 

First Method. WHEN THE SIDES INTERSECT. 

Draw the lines C and A — about 3 inches long — forming 
any angle of 45 to 60 degrees. With as a center and any con- 
venient radius — about 2 inches — draw an arc intersecting the sides 
of the angle at E and F. With E and F as centers and a radius of 
I \ or If inches, describe short arcs intersecting at 7. A line D. 
drawn through the points and I, bisects the angle. 

In solving this problem the arc E F should not be too near the 
vertex if accuracy is desired. 

Proof. The central angles A D and DOC are equal be- 
cause the arc E F is bisected by the line D. The point I is equally 
distant from E and F. 

Second Method. WHEN THE LINES DO NOT INTERSECT. 

Draw the lines A C and E F about 4 inches long making an 

125 






MECHANICAL DRAWING 




126 



MECHANICAL DRAWING 61 

angle approximately as shown. Draw A r C ; and' E f F f parallel to 
A C and E F and at such equal distances from them that they will 
intersect at 0. Now bisect the angle C F' by the method given in 
Problem 8. The line R bisects the given angle. 

Proof. Since A / C is parallel to A C and E' F' is parallel to 
E F, the angle C F' is equal to the angle formed by the lines 
A C and E F. Hence as R bisects angle C F' it also bisects 
the angle formed by the lines A C and E F. 

Problem 10. To divide a line into any number of equal parts. 

Let A C — about 3f inches long — be a given line. Suppose 
it is desired to divide it into 7 equal parts. First draw the line A J 
at least 4 inches long, forming any convenient angle with A C. On 
A J lay off, by means of the dividers or scale, points D, E, F, G, etc., 
each | inch apart. (If dividers are used, the spaces need not be 
exactly \ inch.) Draw the line J C and through the points D, E, 
F, G, etc., draw lines parallel to J C. These parallels will divide 
the line A C into 7 equal parts. 

Proof. If a series of parallel lines, cutting two straight lines, 
intercept equal distances on one of these lines, they also intercept 
equal distances on the other. 

Problem 11. To construct a triangle having given the three sides. 

Draw the three sides, A C, 2f inches long; E F, ly| inches long; 
and M N, 2 T 3 g- inches long. 

Draw R S equal in length to A C. With R as a center and a 
radius equal to E F describe an arc. With S as a center and a radius 
equal to M N draw an arc cutting the arc previously drawn, at T. 
Connect T with R and S to form the triangle. 

Problem 12. To construct a triangle having given one side and 
the two adjacent angles. 

Draw the line M N 3j inches long and draw two angles A D 
and E F G about 30 degrees and 60 degrees respectively. 

Draw R S equal in length to M N and with R as a vertex and 
R S as one side construct an angle equal to A D. In a similar 
manner construct at S an angle equal to E F G. Draw lines from 
R and S through the two established points until they meet at T. 
The triangle R T S will be the required triangle. 

Lettering. Draw the pencil lines and put in the lettering as 
in plates already drawn. 



127 



MECHANICAL DRAWING. 

Inking. In inking Plate V, follow the principles previously 
used and do not make certain lines dotted until sure that they should 

be dotted. 

After inking the figures, ink in the border lines and the lettering 

as already explained. 

PLATE VI 

Penciling. Lay out this plate in the same manner as the pre- 
ceding plates. 

Problem 13. To describe an arc or circumference through three 

points not in the same straight line. 
Locate the three points A, B, and C with a distance between 
1 and B of about 2 inches and a distance between A and C of about 
2\ inches. Connect A and B and A and C. Erect perpendiculars 
to the middle points of A B and A C as explained in Problem 1. 
Now draw light pencil lines connecting the intersections / and J 
and E and F. These lines will intersect at 0. 

With as a center and a radius equal to the distance A, 
describe the circumference passing through A, B, and C. 

Proof. The point is equally distant from A, B, and C, since 
it lies in the perpendiculars to the middle points of A B and A C. 
Hence the circumference will pass through A, B, and C. 
Problem 14. To inscribe a circle in a given triangle. 
1 )ra\v the triangle L M N of any convenient size. M N may 
be made 3 J inches, L 31, 2J inches, and L N, 3h inches. Bisect 
the angles 31 L X and L 31 N by the method used in Problem 8. 
The bisectors 31 1 and L J intersect at 0, which is the center of the 
inscribed circle. The radius of the circle is equal to the perpen- 
dicular distance from to one of the sides. 

Proof. The point of intersection of the bisectors of the angles 
of a triangle is equally distant from the sides. 

Problem 15. To inscribe a regular pentagon in a given circle. 
With as a center and a radius of about IV inches, describe 
the given circle. With the T-square and triangles draw the center 
lines I C and E F perpendicular to each other and passing through 
(). Bisect one of the radii, O C, at // and with this point as a center 
and a radius If K, describe the arc E P. This arc cuts the diameter 
.1 ' .t P. With E as a center and a radius K P, draw arcs cutting 



128 



MECHANICAL DRAWING 



63 



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129 



MECHANICAL DRATaXG 

the cin u inference at L and Q. With the same radius ?vnd centers 
and (), draw the arcs cutting the circumference at M and X. 

The pentagon is completed by drawing the chords E L, L M % 
MX. NQ, and Q /:. 

Problem 16. To inscribe a' regular hexagon in a given circle. 

With as a center and a radius of If inches draw the given 
circle. With the T-square draw the diameter AD. With D as 
a center, and a radius equal to D, describe arcs cutting the cir- 
cumference at C and E. Now with C and E as centers and the 
.same radius, draw the arcs, cutting the circumference at B and 
F. Draw the hexagon by joining the points thus formed. 

Therefore, in order to inscribe a regular hexagon in a circle, 
mark off chords equal in length to the radius. 

To inscribe an equilateral triangle in a circle the same method 
may be used, the triangle being formed by joining the opposite 
vertices of the hexagon. 

Proof. Since the triangle C D is an equilateral triangle by 
construction, the angle C D is one-third of two right, angles and 
<)ne->ixth of four right angles. Hence arc C D is one-sixth of the 
circumference and the chord is a side of a regular hexagon. 

Problem 17. To draw a line tangent to a circle at a given point 
on the circumference. 

With as a center and a radius of about 1J inches draw the 
given circle. Assume some point P on the circumference and join 
the point P with the center 0. By the method given in Problem 6, 
Plate IV, construct a perpendicular to P 0, which perpendicular 
will be the desired tangent to the circle at the point P. 

Proof. A line perpendicular to a radius at its extremity is 
tangent to the circle. 

Problem 18. To draw a line tangent to a circle from a point 
outside flic circle. 

With as a center and a radius of about 1 inch draw the given 
circle. Assume P some point outside of the circle about 2-V inches 
From the center. Draw a straight line passing through P md 0. 
Bisect P and with the middle point Fas a center describe the circle 

ing through P and 0. Draw a line from P through the inter- 
90 ction <>f the two circumferences C. The line P C is tangent to. the 
cavm circle. Similarly P E is tangent to the circle. 



130 



MECHANICAL DRAWING 65 

Proof. The angle P C is inscribed in a semicircle and hence 
is a right angle. Since P C is a right angle, P C is perpendicular 
to CO. The perpendicular to a radius at its extremity is tangent to 
the circumference. 

Inking. In inking Plate VI, the same method should be fol- 
lowed as in previous plates. 

PLATE VII 

Penciling. Lay out this plate in the same manner as the pre- 
ceding plates. 

Problems 19 and 20. To draw an ellipse when the axes are given. 

First Method. Draw the lines L M and C D about 3 J and 2\ 
inches long respectively, making C D perpendicular to L M at its 
middle point P and having C P = P D. The two lines, L M and 
C D, are the axes. With C as a center and a radius L P equal to 
one-half the major axis, draw the arc, cutting the major axis at 
E and F. These two points are the foci. 

Now locate several points on P M, such as A, B, and G. With 
E as a center and a radius equal to L A, draw arcs above and below 
L M. With F as a center and a radius equal to A M describe short 
arcs cutting those already drawn as shown at N. With E as a center 
and a radius equal to L B draw arcs above and below L M as before. 
With F as a center and a radius equal to B M, draw arcs intersecting 
those already drawn as shown at 0. The point R and ethers are 
found by repeating the process. The student is advised to find at 
least 12 points on the curve — 6 above and 6 below L M . These 
12 points with L, C, M, and D will enable him to draw the curve. 

After locating these points, draw a free-hand curve passing 
through them. 

Second Method. Draw the two axes A B and P Q in the same 
manner as in the first method. With as a center and a radius 
equal to one-half the major axis, describe a circie. Similarly with 
the same center and a radius equal to one-half the minor axis, describe 
another circle. Draw any radii such as C, D, E, F, etc., 
cutting both circumferences. These radii may be drawn with the 
60 and 45 degree triangles. From C, D, E, and F, the points of 
intersection of the radii with the large circle, draw vertical lines and 
from C", D', E', and F' the points of intersection of the radii with 



131 






MECHANICAL DRAWING 






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132 



MECHANICAL DRAWING 67 

the small circle, draw horizontal lines The intersections of these 
iines are points on the ellipse. 

Draw a free-hand curve* passing through these points; about 
five points in each quadrant will be sufficient. 

Problem 21. To draw an ellipse by means of a trammel. 

As in Problems 19 and 20, draw the major and minor axes, 
U V and X Y. Take a slip of paper having a straight edge and 
mark off C B equal to one-half the major axis, and D B equal to 
one-half the minor axis. Place the slip of paper in various positions 
keeping the point D on the major axis and the point C on the minor 
axis. If this is done, the point B will mark various points on the 
curve. Find as many points as necessary and sketch the ellipse. 

Problem 22. To draw a spiral of one turn in a circle. 

Draw a circle with the center at and a radius of 1^ inches. 
Locate twelve points, •§■ inch apart on the radius A and draw 
circles through these points. With the 30-degree triangle, draw radii 
OB, OC, OD, etc., 30 degrees apart, thus forming 12 equal parts. 

The points on the spiral are now located; the first is at the 
center 0; the next is at the intersection of the line B and the first 
circle; the third h. at the intersection of C and the second circle; 
the other points are located in the same way. Sketch in pencil a 
smooth curve passing through these points. 

Problem 23. To draw a parabola when the abscissa and ordinate 
are given. 

Draw the straight line A B — about three inches long — as the 
axis, or abscissa of the parabola. At A and B draw the lines EF 
and C D perpendicular to A B, and with the T-square draw E C 
and F D, 1 J inches above and below A B, respectively. Let A be 
the vertex of the parabola. Divide A E and E C into the same num- 
ber of equal parts. Through R, S, T, U, and V. draw horizontal 
lines and connect L, M, N f 0, and P, with A. The intersections 
of the horizontal lines with the oblique lines are points on the curve. 
For instance, the intersection of A L and the line V is one point and 
the intersection of A M and the line U is another. 

The lower part of the curve A D is drawn in a similar manner. 

Problem 24. To draw a hyperbola when the abscissa E X. the 
ordinate A E, and the diameter X Y are given,. 

*See Page 1G, Mechanical Drawing, Part I. 

133 



MECHANICAL DRAWING 

Draw F F about 3 inches long and mark the point X, 1 inch 
from E and the point Y, 1 inch from X. With the triangle and 
T-square, draw the rectangles A B D C and PQ R such that A B 
IS 1 inch in length and .1 C, 3 inches in length. Divide A E and A B 
into the same number of equal parts. Connect Y with the points 
F, U t and T, on A E, and connect X with Z,, M, and N, on ^4 J5. 
The first point on the curve is at A; the next is at the intersection of 
T Y and L X; the third is at the intersection of U Y and M X. 
The remaining points are found in the same manner. Repeat the 
process tor X C and the right-hand curve P Y Q. 

Inking. In inking the figures on this plate, use the French or 
Irregular curve and make full lines for the curves and their axes. 
Dot the construction lines as usual. Ink in all the construction 
lines used in finding one-half of a curve, and in Problems 19, 20, 23, 
and 24 leave all construction lines in pencil except those inked. In 
Pioblems 21 and 22 erase all construction lines not inked. The 
trammel used in Problem 21 may be drawn in the position shown, 
or outside of the ellipse in any convenient place. 

The same lettering should be done on this plate as on previous 
plates 

PLATE VIII 

Penciling. In laying out Plate VIII, draw the border lines 
and horizontal and vertical center lines as in previous plates, divid- 
ing the plate into four spaces. 

Problem 25. To construct a cycloid when the diameter of the 
generating circle is given. 

Vs ith 0' as a center and a radius of f- inch draw a circle, and, 
tangent to it, draw the indefinite horizontal straight line A B. Divide 
the circle into any number of equal parts — 12 for instance — and 
through these points of division C, D, E, F, etc., draw horizontal 
lines. Now with the dividers set so that the distance between the 
points is equal to the chord of the arc CD, mark off the points L, 
M, N,0,P, on the line A B, commencing at the point il. At these 
points erect perpendiculars to the center line X 0' which is the line 
of centers of the generating circle as it rolls along the line A B. With 
the intersections Q, R t 8, T, etc., as centers describe arcs of circles 

bown. The points on the cycloid will be the intersections of 



134 



MECHANICAL DRAWING 



69 




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135 



MECHANICAL DRAWING 

ares and the horizontal lines drawn through the points C, D, £ ; 
Thus the intersection of the are whose center is Q and the 
horizontal line through C is a point J on the curve. Similarly, the 
intersection of the arc whose center is R and the horizontal line 
through D is the point K on the curve. The remaining points on 
the left, as well as those on the right, are found in the same manner. 
at accuracy in this curve, the circle should be divided 
into a large number of equal parts, because the greater the number 
of divisions the less the error due to the difference in length be- 
tween a chord and its arc. 

Problem 26. To construct an epicycloid when the diameter of the 
generating circle and the diameter of the director circle are given. 

The epicycloid and the hypocycloid may be drawn in the same 
manner as the cycloid if arcs of circles are used in place of the hori- 
zontal lines. With as a center and a radius of j inch describe 
a circle. Draw the diameter E F of this circle and produce E F 
to G such that the line F G is 2f inches long. With G as a center 
and a radius F G, describe the arc A B of the director circle. With 
the same center G, draw the arc P Q which will be the path of the 
center of the generating circle as it rolls along the arc .4 B. Now 
divide the generating circle into any number of equal parts — twelve 
for instance — and through the points of 'division H, I, L, M, and N t 
draw arcs having G as a center. With the dividers oet so that the 
distance between the points is equal to the chord H I, mark off dis- 
tances on the director circle A F B. Through thes^ points of division 
A', S, T, U, etc., draw radii intersecting the arc P Q in the points 
II' . S' } T f , etc., and with these points as centers describe arcs of circles 
as in Problem 25. The intersections of these arcs with the arcs 
already drawn through the points H, I, L, M, etc., are points on the 
epicycloid. Thus the intersection of the circle whose center is R' 
with the arc drawn through the point if is a point upon the curve. 
Also the arc whose center is S' with the arc drawn through the point 
/ is another point on the curve. The remaining points are found 
1)V repeating this process. 

Problem 27. To dram an hypocycloid when the diameter of the 
/ circle and the radius of the director circle are given. 

With C as a center and a radius of 4 inches describe the arc 
/. F. which is the arc of the director circle. Now with the s-ime 



136 



MECHANICAL DRAWING 71 

center an J a radius of 3J inches, describe the arc A B, which is the 
line of centers of the generating circle as it rolls on the director circle. 
With 0' as a center and a radius of f inch describe the generatiug 
circle. As before, divide the generating circle into any number 
^f equal parts — 12, for instance — and with these points of division 
L, M, N, 0, etc., draw arcs having C as a center. Upon the arc 
E F, lay off distances Q R, R S, S T, etc., equal to the chord Q L. 
Draw radii from the points R, S, T, etc., to the center of the director 
circle C and describe arcs of circles having a radius equal to the radius 
of the generating circle, using the points G, I, J, etc., as centers. As 
in Problem 26, the intersections of the arcs are the points on the 
hypocycloid. By repeating this process, the right-hand portion of 
the curve may be drawn. 

Problem 28. To draw the involute of a circle when the diameter 
of the base circle is known. 

With the point as a center and a radius of 1 inch, describe the 
base circle. Divide the circle into any number of equal parts — 16, 
for instance — and draw radii to the points of division. At the point 

D, draw a light pencil line perpendicular to D. This line will 
be tangent to the circle. Similarly at the points E, F, G, H, etc., 
draw tangents to the circle. Set the dividers so that the distance 
between the points will be equal to the chord of the arc C D, and 
measure this distance from D along the tangent. From the point 

E, measure on the tangent a distance equal to two of these chords; 
from the point F, three divisions; and from the point G, four divisions. 
Similarly, measure distances on the remaining tangents, each time 
adding the length of the chord. This will give the points L, M, N, 
P, etc., to T. The curve drawn through these points will be the 
involute of the circle. 

Inking. Observe the same rules in inking Plate VIII as were 
given for Plate VII. In Problems 25 and 26 the arcs and lines 
used in locating the points of the other half of the curve may be left 
in pencil. In Problem 28, all construction lines should be inked. 
After completing the problems the same lettering should be done on 
this plate as on previous plates. 



137 



MECHANICAL DRAWING 

PART III 

PROJECTIONS 

ORTHOGRAPHIC PROJECTION 

Definitions. Projection. The word projection means to throw 
forward. In mechanical drawing, the significance is to throw forward 
in straight lines. Projection really means, therefore, either the 
act or the result of projecting parallel rays from the surface of a 
body and of cutting these rays with a plane, so as to obtain on the 




Fig. 95. Body and Its Projection 

plane a shape corresponding point for point with that of the body. 
The rays are called projecting lines. A plane may be considered 
transparent, since it is a flat surface having no thickness. 

View. In Fig. 95 a body is shown as projecting from its sur- 
face projection lines, and these lines are cut by a plane. By con- 
necting the points on the plane made by the projection lines the 



139 



74 



MECHANICAL DRAWING 



projection of the body is formed, and it corresponds in shape with 
the b< '<ly it-elf. A projection of this kind is called a view, this name 
being given it on account of the fact that an observer on the same side 
pf the body as the projection plane would get this view. 

It can readily be seen that one view only will not give a com- 
plete picture of a solid object. Usually two or more views are 
necessary, according to the complication of the object or body. 
When two or three views are shown, they are pictured on two or 

three planes at right an- 
gles to each other. In 
this way views of two 
or three sides are shown, 
and this is usually suffi- 
cient to give the idea of 
the complete form of the 
object. 

Orthographic. The 
word orthographic means 
at right angles, and in 
mechanical drawing, in 
connection with the word 
projection, it means that 
two or more views are 
projected on planes at 
right angles with each other. The various views of a body have 
special names — those showing vertical faces are called elevations, 
Buch as front, side, end or rear elevation; a view of the top of a 
body is called a plan or p>lan view; and a view of the under side, a 
bottom vt> 

Third- Angle Projection. In Fig. 96 is shown three faces of a 
body projected on three planes — the top view on the top plane, 
the front view on the front plane, and the end view on the end plane. 
It will be seen that the same body is represented as projecting rays 
in three directions, and thus the three projections, or views, are 
obtained. It will also be seen that the three planes with their views 
b en brought into one plane, that is, the surface of the paper. 
Tlii> brings the top view directly above the front view, and the end 
view to the right of the front view. The above is a definition of 













Top 

View 

y 










/ 1 


1 




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Front 






End 






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View 


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Fig. 9G. Projections of Top, Front, and End of Body 



140 



MECHANICAL DRAWING 



75 



true projection, usually called third-angle projection, and is the 
method used by practically all draftsmen in this country. 

First-Angle Projection. There is, however, a method called 
first-angle projection, used but little now in this country, although 
formerly in almost general use. Because draftsmen may have to 
do at times with old drawings or drawings made in foreign countries, 
it is well for them to understand first-angle projection. This method 




Fig. 97. Body and Its First-Angle Projections 

brings the front view, or elevation, above the top view, or plan, 
the end view being at the right of the front view. Fig. 97 shows 
this method of first-angle projection. 

Comparison of Third- and First-Angle Projection. Perhaps a 
short explanation will make clear the meaning of third- and first- 
angle projection. In geometry, when two planes intersect at right 
angles, the angles are designated as first, second, third, and fourth, 
as numbered in Fig. 97. In first-angle projection, the body is placed 
in angle 1, and a top view is projected on a plane under the body 



141 






MECHANICAL DRAWING 



This ihe projection lines back through the body, instead 

of throwing them out from The surface. In fact, by this method, 
the body is supposed To Turn itself inside out, an absurdity which 
led To The general abandonment of the meThod in this counTry. 
Third-angle projection places a body in angle 3, and projects a top 
view on To The plane above it, and a front view on to the plane in 
front of it. This is True projection. 

Projection Methods. When a drawing is made by projection, 
an object is represented just as it would be seen if one eye were 
closed and the other were directly over each point of the object at 
the same Time. As an illustration of this, place a box on a table 
and a piece of ground glass a few inches in front of it. Now, stand 




Fig. 9S. Visual Method of Finding Projection 

so that one eye will come directly in line with one corner a, Fig. 98. 
Make a dot at a\ where the line from the eye to the corner a passes 
through the glass. Next, move the eye until it is directly in line 
with the corner b of the box, and put a dot at 61 where the line 
from the eye to the corner b passes through the glass. Repeat 
this process, putting dots on the glass at Ci and d x where the lines 
from the eye to the corners c and d pass through the glass. Now, 
connect the points a u b u c u and d l} and the complete projection of 
the front of the box will be shown by The figure on The glass. This 

The fir-t four figures in this textbook, Figs. 95, 96, 97, and 98, 

ietoriaJ views given to show the Student clearly how the views of objects 

are projected. The student in drawing orthographic projections does not need 

t«. draw tin- pictorial views, but simply the projections, as illustrated in Figs. 99 



14.? 



MECHANICAL DRAWING 



77 



figure is a rectangle, and is the same shape and size as the front 
of the box. 

It is readily seen that from this one projection drawing, or view, 
no idea of the depth of the box is given, although the width and 
height are correctly shown. A top, or plan, view must now be 
made to show the depth of the box. Place another piece of ground 
glass a few inches above the box and, with the eye directly over each 
separate corner of the top, 
repeat the process of making 
the four dots, representing 
each top corner. Connect 
these four dots, and the fig- 
ure thus formed represents 
the top projection, or plan 
view, of the box. Now, ar- 
range the two pieces of glass, 
as shown in Fig. 99. The 
box being removed, the upper 
glass is simply lowered to the 
table, and the front glass is 
turned from the bottom for- 
ward and up, and laid direct- 
ly below the upper glass. 

This position of the fig- 
ures represents the two pro- 
jections — front elevation and 
plan — just as they would be 
drawn by a draftsman on a 
sheet of drawing paper. The 
width of the box is shown in 
both views, and being the 
same in each, the front elevation and plan are both of equal width, 
and therefore each point in the plan is directly over the corre- 
sponding point in the front elevation. In more complicated objects, 
where the complete idea cannot be obtained from the front eleva- 
tion and plan views, an end view or both end views must be shown 
as in Fig. 100, which represents the projections of a box with a 
curved top. These end views are obtained by taking two or more 









(0 
10 


Plan 




■ 




CO 
(0 

k 






front 
Elevation 



Fig. 99. 



Plan and Elevation of Cox Shown in 
Fig. 98 



143 



7- 



MECHANICAL DRAWING 



pieces of ground glass, placing them one in front of each end, and 
then drawing the projections. This is done, as in the cases of the 





Fig. 100. Plan, Elevation, and End Views of a Box with a Curved Top 



Heor Vie w 




(Left) Side View 
(O r Sect i on) 



Top View 




Front Viet 




Bo t torn Vi e w 



(Right) Side View 
(Or- Section) 



Fig. 101. Six Views of Object 
Pennsylvania Railroad Company, Altoona, Pennsylvania 

from elevation and plan, by making several dots for the shape of 
top, and drawing a curved line through these dots. The two 



144 



MECHANICAL DRAWING 



79 



end views are placed as shown — the right-hand view at the right 
of the front view, and the left-hand view at the left. This gives 
the proper arrangement of the views as a draftsman would work 
them out on paper. 

In Fig. 101 is represented a practical case where the object 
is sufficiently complicated to require a view of each of its six faces. 
As will be seen in the figure, six views are shown — front, top, 




Fig. 102. Folding Out of the Projection Planes Into the Plane of the Surface of 

the Drawing Paper 

Courtesy of Pennsylvania Railroad Company, Altoona, Pennsylvania 

bottom, right side, left side, and rear. In Fig. 102 is represented 
the method of folding out the projection planes after the faces of 
the object have been projected on them, in order to have them all 
in one plane — that of the surface of the drawing paper, as shown 
in Fig. 101. 

Drawing the Projection on Paper. From the explanation just 
given, it will be seen that the projection views are all of the same 
size as the faces of the object they represent. They can, therefore, 



145 



so 



MECHANICAL DRAWING 




Horizontal Plane 



Vertical Plane 



be drawn just as readily on a sheet of drawing paper without the 
of the ground glass. For the front view, measure the four 
f n nit edges < »f the object, and lay off on the paper a figure of the same 
shape as the front of the object. Repeat the process for the top 
of the object, obtaining the top view, or plan; and for each end of 
the object, obtaining the end view, or side views. The bottom and 

rear views can be placed in 
the same way. Draw the plan 
view with its four corners di- 
rectly over the four corners of 
the front view, and the bot- 
tom view with its four cor- 
ners directly under. Draw the 
right end, or side, view with 
its four corners directly to the 
right of the four corners of the 
front elevation, and the left 
end, or left side, view and rear 
view, with their corners di- 
rectly to the left of the cor- 
ners of the front view. 

Projection Lines. As each 
projected point of an object 
shown in plan view must be 
directly over the projection of 
the same point in the front 
elevation, a vertical dotted 
line will connect these points, 
a- projected in pairs; and as each projected point in an end 
view must be directly opposite the projection of the same point in 
the front elevation, a horizontal dotted line will connect these 
points, as projected in pairs. These dotted lines are called pro- 
jection or construction lines. 

(iround Line. Having the two planes, at right angles, on which 

the front, elevation and plan are represented, when the top plane is 

turned up to bring the plan above the front elevation, as repre- 

Bented on the surface of the drawing paper, it revolves on the inter- 

Og line of the two planes as an axis. This intersecting line xy 



Ground Lino, xy, at Intersection 

ui Horizontal and Vertical Planes 



14G 



MECHANICAL DRAWING 



81 



in Fig. 103, is called the ground line, and this is usually abbreviated 
to GL. The projections may be placed at any convenient distance 
above or below the GL, unless these distances are given in any prob- 
lem. In beginning all ordinary projection work, it is customary 
to show the GL as a horizontal line between the front elevation and 
plan views, and the projection of any pair of points in the front 
and plan views are always in a line perpendicular to the GL. This 
is evident from the fact that the points in the plan view are directly 



<f~ 






v 



Fig. 104. Typical Projections 

over the corresponding points in the front elevation. Although 
the ground line is usually used in learning the subject of projections, 
it is customary to omit it in practical work. 

Rules of Projection. (1) If a surface is perpendicular to either 
plane of projection, its projection on that plane is simply a line — 
a straight line if the surface is plane, a curved line if the surface is 
curved. 

(2) The projected view of any point of any object on a plane 
%S in a perpendicular drawn to the plane through the point of the object. 



147 






.MECHANICAL DRAWING 



(3) If a straight line is perpendicular to a plane, its projection 
on that plane is a point; and if the straight line is parallel to the plane, 
the projection is a line equal in length to the line itself and makes the 
same angle with the ground line. 

(4) All points on any object at the same height above its base 
must appear in the front elevation at the same distance below the ground 
jinr, and all points on an object at the same distance back of the front 
face must appear in the plan at the same distance above the ground 
line. 

Typical Examples of Projection. Figs. 104 and 105 show clearly 
several ideas of plan and elevation. In such work as this, it is 




Fig. 105. Typical Projections 

customary to call the vertical plane on which the front elevation 
is drawn V, and the horizontal plane on which the plan is drawn H. 

A = a point A" below H, and B" in front of V 

B = a square prism resting against V, two of its faces parallel 
to // 

('= a circular disk in space para/lel to H 

I> --- a triangular card in space parallel toH 

K= a cone with its base resting against V 

F= a cylinder perpendicular to #, and with one end resting 
against // 



148 



MECHANICAL DRAWING 



83 



G = a line perpendicular to V 

H = & triangular pyramid back of F,with its base resting against H 

PRACTICAL PROBLEMS IN PROJECTION 

1. Square Bar. Fig. 106 represents a square bar. A is the 
front elevation, and shows the length and width of the bar, but not 
the thickness. There must then be another view. B is the plan, 




Fig. 106. Projections of 
Square Bar 



Fig. 107. Projections of 
Round Bar 



Fig. 108. Projections of 
Hexagonal Bar 



and shows the width and thickness of the bar. From these two 
views the complete form of the bar is obtained and no other views 
are necessary when such is the case. In all working drawings, only 
as many views are shown as is necessary to determine the complete 
form of the object being drawn. 

2. Round Bar. Fig. 107 represents a round bar. The front 
elevation A, shows the width and height of the bar, but does not 
show that it is round. The plan B, shows the circular top of the 
bar and of the proper diameter. In this problem, in addition to the 



149 






MECHANICAL DRAWING 



dotted projection lines connecting points in plan and elevation, 
advisable to put in dot and dash lines for center lines. Pro- 
jection lines and center lines are construction lines, 
and may be erased when the drawing is finished, 
unless otherwise ordered. 

3. Hexagonal Bar. Fig. 108 represents a 
hexagonal bar. In this case, center lines should 
be drawn. The front elevation A, shows the 
length of the bar, and the plan B, shows the form 
and the distance between faces. The vertical lines 
in the front elevation show the corners of the 
hexagonal form while both views show the dis- 
tance from corner to corner of the hexagonal top. 

4. Hexagonal Xirt. Fig. 109 represents a 
al nut. Center lines should be drawn here also. The front 

elevation A, shows the thickness and width of the nut, and the cir- 




/: 



Projection 
vigonul Xut 





Fig 110. Projectioi 

under with Circular Hole 



Fig. 111. Projections of Frusta 
of Square Pyramid 



Clllar hole is shown by heavy dotted lines. Holes are always rep- 
resented in this way. The plan />, shows the shape of the top of 
the nut, and also the shape of the hole. 



150 






MECHANICAL DRAWING 



85 



^ N S 



5. Cylinder with Circular Hole. Fig. 110 represents a cylinder 
with a circular hole passing part way through. Center lines are 
needed here, and in fact where any circle, hexagon, octagon, or other 
shape except a square or rectangle occurs. The front elevation A, 
shows the height and width of the cylinder, 
and the depth and width of hole. The plan 
B, shows the top of the cylinder, its diam- 
eter, and the diameter of the hole. 

6. Frustum of Square Pyramid. Fig. Ill 
represents a block in the form of a frustum 
of a square pyramid. The front elevation A, 
shows the height of the block, and the width 
of the top and bottom faces. The plan B, 
shows the width and depth of the top and 
bottom faces, and also the edges connecting 
these faces of the frustum. 

7. Square Bar with Cylindrical Portion. 
Fig. 112 represents a square bar with a por- 
tion forged to a cylindrical form. The front 
elevation A, shows the length and width of 
the bar, and also the length and width of the 
cylindrical portion. The plan B, shows the 
square top, and by the dotted circle shows 
the shape of the cylindrical portion. The 
fact that this circle is dotted means that the 
cylindrical portion does not come clear 
through to the top. A bottom view C, is 
also shown here, as it gives a better idea of 
the complete form of the bar. Enough views 
should always be shown by the draftsman 
to give the workman a clear idea of what 
he is to make. 

8. Circular Ring Made from Round Rod. 
a circular ring made from a round rod. 




Fig. 112. Projections of 
Square Bar with Cylin- 
drical Portion 



Fig. 113 represents 
The front elevation A, 
shows the thickness and the diameter of the ring, and the "olan B, 
shows the circular form. 

9. Block with Number of Different Dimensions. Fig. 1X4 rep- 
resents a block with a number of different dimensions. The block 



151 






MECHANICAL DRAWING 



been turned down in such a way that there are five different 
diai 3 shown. All these diameters, and the lengths between, 

may be shown in the front elevation A. From this view, only the 
forms of the cross-section could not be ascertained. Some might 
be square, some hexagonal, or some cir- 
cular, but the plan B shows that all are 
circular. 

Summary. The principles of projec- 
tion which have been used so far, may 
be stated as follows : 

(1) If a line is parallel to either the verti- 
cal or horizontal plane, its actual length is shown 
Dn that plane, and its other projection is parallel 
to the ground line. 





Fig. 113. Projections of Circular Ring 



Fig. 114. Projections of Turned Block 



(2) A line oblique to either plane has its projections on that plane shorter 
than the line itself, and its other projection oblique to the ground line. 

(3) No projection can be longer than the line itself. 

(4) If two lines intersect, their projections must cross, and the point of 
nog in the front elevation must be directly under the point of crossing in 

Ian. 

(5) A plane surface, if parallel to either plane, is shown on that plane 

and shape; if oblique, it is shown smaller than the true size, and 
if perpendicular it is shown as a straight line. 

I ; raUel in space have both their vertical and horizontal pro- 

jections parallel. 



152 



MECHANICAL DRAWING 



87 



TRUE LENGTH OF LINES 

Principles. If a line is parallel to a plane, its projection on 
that plane will be equal in length to the line itself, as represented 
in Fig. 115. If a line is perpendicular to a plane, its projection on 

i 1 



Fig. 115. Projections of a Line Parallel 
to Plane 

the plane will be a point, as repre- 
sented by the cross in Fig. 116. If 
a line is inclined to a plane, its pro- 
jection on that plane will be shorter Fig. ii6. 
than the line itself, as represented 
in Fig. 117. If a line is parallel to the horizontal or vertical plane, 
its projection on the other plane will be parallel to the ground line, 
as represented in Fig. 118. A line inclined to both the horizontal 



Projections of a Line Perpen- 
dicular to Plane 





-I* 



Fig. 117. 



Projections of a Line Inclined 
to Plane 



Fig. 118. Projections of Lines Paral- 
lel to Ground Line 



and vertical planes will not show its true length in either projec- 
tion, as represented in Fig. 119. In a case like the one last men- 
tioned, the true length of the line is found by revolving the line 
until it is parallel to one of the planes. Then, its projection on 
that plane will be its true length. 



153 



Sg MECHANICAL DRAWING 

True Length by Revolving Horizontal Projection. In Fig. 120 
is shown the horizontal and vertical projections of the line AB, 

and to find the true length 
of the line itself proceed as 
follows : Swing the horizon- 
tal projection A h B h about 
one end A h as a pivot, 
until it is parallel to the 
ground line. Project the 
new point Bi h downward 
to a point on the vertical 
plane to a line drawn from 
B v parallel to the ground 
line, locating the point Bi. 
The line connecting Bi 
and A v is the true length 
desired, since the true 
length of a line is always 
shown by its projection on 
a plane when the line is parallel to that plane. 

True Length by Revolving Vertical Projection. In Fig. 121 
is shown the method of finding the true length of the same line as 







Kg. 119. 



True Length of Inclined Line not Shown 
in Its Projections 




rue Length of a Line by Revolv- 
ing Horizontal Projection 




Fig. 121. True Length of a Line by 
Revolving Vertical Projection 



in Pig. 120, but by revolving the vertical projection. The method 
is the same. Revolve A IV about the end B p as a pivot until it is 
parallel t<> the ground line, and then project A x v up to A* on the 



154 



MECHANICAL DRAWING 



89 



horizontal plane at the same distance from the ground line as A h . 
The true length is then shown on the horizontal plane by the line 
connecting A\ and B h . Projection lines representing the true 
length are always shown as dot and dash lines, as in Fig. 120 and 121. 

REPRESENTATION OF OBJECTS 

Rectangular Prism or Block. In Fig. 122 there is represented 
a rectangular prism or block, whose length is twice its width. The 
elevation shows its height. 
As the block is placed at an 
angle, three of the vertical 
edges will be visible, and the 
fourth, invisible. In mechan- 
ical drawing, the edges, 
which in projection form a 
part of the outline or con- 
tour of the figure, must al- 
ways be visible, hence are 
always drawn as full lines, 
while the lines or edges which 
are invisible are drawn dot- 
ted. The plan shows what 
lines are visible in elevation, 
and the elevation determines 
what are visible in plan. In 
Fig. 122, the plan shows that 
the dotted edge AB is the 
back edge, and in Fig. 123, 
the elevation shows that the 
dotted edge CD is the lower edge of the triangular prism. In gen- 
eral, if in elevation an edge projected within the figure is a back 
edge, it must be dotted, and in plan, if an edge projected within 
the outline is a lower edge, it is dotted. 

Triangular Prism or Block. The end view shown in 
Fig. 123 is obtained by projecting the points of the plan across 
to a plane at right angles to the horizontal and vertical planes, 
then revolving them down through 90 degrees and continuing 
the projections to meet the projection lines drawn across from 



1 \ 
1 \ 
I \ 
1 \ 

1 N 

\ 

1 
1 


i i 







Fig. 122. Projections of a Rectangular Prism or Block 



155 



90 



MECHANICAL DRAWING 



the elevation. Connecting the points thus obtained gives the end 
End or side views of any object are obtained by projection 

in this way. 

Triangular Block 
with Square Hole. The 
plan, elevation, and end 
views of a triangular 
block with a square hole 
from end to end are 
shown in Fig. 124. In 
this case the plan and 
elevation alone would 
not be sufficient to pos- 
itively determine the 
shape of the hole, but 
the end view shows at 
a glance that it is 
square. 




FL'. 123. Projections of a Triangular Prism or Block 



\ 



\ 



^\ 



\ 




134. Projections of a Triangular Block with Square Hole 

ROTATING AND INCLINING OF OBJECTS 
Method of Rotating Object. The natural way to place an 
t to be ahowD by projections would be in the simplest position; 
that is, with an edge or face parallel to either the horizontal or 



156 



MECHANICAL DRAWING 



91 



vertical plane of projection. Sometimes it is necessary, however, 
to draw the views of an object in a position at an angle to the planes. 
In such case it is usually advisable to draw the object parallel to one 
of the planes, and then rotate it to the required position about an 
axis perpendicular to a plane of projection. 

When an object is rotated in this way, about an axis perpen- 
dicular to a plane, its projection on that plane will remain unchanged 




Fig. 125. Plan, Front, and Side Views of a Square Pyramid 

in size and shape, and the dimensions parallel to this axis on the 
other planes will remain the same. 

Pyramid. In Fig. 125, the plan, front, and side views of a 
pyramid are shown, and in Fig. 126 is shown the same pyramid 
after it has been rotated through 30 degrees about an axis per- 
pendicular to the horizontal plane. The height of ^ the pyramid 
has not been altered by this rotation and, therefore, the front and 
side views are the same height as in the original front view. 

Now, if the pyramid in Fig. 125 is rotated about an axis per- 
pendicular to the vertical plane, the front view will not be altered. 



157 



92 



MECHANICAL DRAWING 



and may be copied in the new position at an angle of 30 degrees, 
,«>\vn in Fig. 127. The distances above the ground line to any 
points in the top view arc not altered, and the distances of the various 
points can be taken on the lines projected up from the points of the 
front view with a pair of dividers, or the points can be obtained 
l>v projecting across from the original top view to meet the pro- 
jection lines drawn up from the front view. The side view dimen- 
>i(.n- ;in- not altered, and this view can therefore be obtained in 




Fig. 126. Plan, Front and Side Views after Revolving Pyramid in Fig. 125 
through 30 Degrees with Vertical Plane 

the usual way, by projecting across from the front view, and revolv- 
ing down from the plane at right angles to the horizontal and vertical 
planes the points projected across from the top view. 

C) Under in Inclined Position to Horizontal Plane. As shown 
in Fig. 128, first draw the plan, a circle, at A. Then draw the 
rectangle at />'. representing the front view. Now, draw- the rec- 
tangle at C, representing the front view at the desired angle. This 
rectangle C is the same .size as the view at B, since the cylinder 



158 




Fig. 127. Plan, Front, and Side Views after Revolving Pyramid in Fie l* 

through 30 Degrees with Horizontal Plane 




Fig. 128. Projections of Cylinder Inclined to Horizontal Plar 



159 



94 



MECHANICAL DRAWING 



has simply been inclined to the horizontal plane, but kept parallel 
be vertical plane. The point D, the center of the circle forming 
the base of the cylinder, is projected up to the point E, and with 
this point as a center, a circle representing the plan view of the base 
is drawn. Then from F project up to G, and with this point as 
a center draw the circle representing the plan view of the top of the 




1 29. Mot hod of Finding the Projection, in the Form of an Ellipse, of the Top of a 
Cylinder Greatly Inclined to a Plane 

cylinder. Connecting these two circles with horizontal lines HI 
and J I\, representing the sides of the cylinder, completes the plan 
view, and the problem is finished. 

As the cylinder is at an angle with the horizontal plane, it 
will be seen that the top and bottom of the cylinder in the plan 
view are not circles, but ellipses. It is, however, customary to draw 
them with the compass, as circles, when the angle of the cylinder 
with the plane is not great. 



160 



MECHANICAL DRAWING 95 

Cylinder Greatly Inclined to Horizontal Plane. In Fig. 129 
the plan and front elevation of the top of the cylinder are drawn 
at the desired angle with the horizontal plane at A and B, respec- 
tively. The plan view at A is then transferred to C. In each 
of these plan views divide the lower semicircle into a number of 
equal parts, eight in this case. From the view of A, project the 
points — 8, parallel to the center line, down to EF, and then project 
across to the projection lines drawn vertically down from the points 
— 8 in C. The points of intersection of projection lines, corre- 
spondingly numbered, form the shape of the ellipse representing 
the top of the side view of the inclired cylinder D, and the ellipse 
drawn through these points completes this view. The side lines 
of the cylinder may now be drawn, and the curve representing the 
bottom of the side view may easily be copied 'from the lower half 
of the ellipse representing the top view. When the points have 
been located, the ellipses may be drawn through them with the aid 
of an irregular curve. 

ILLUSTRATIVE EXAMPLES 

1. Construct plan and elevation of a regular hexagonal pyramid. 
It is evident that two distinct geometrical views are necessary to 
convey a complete idea of the form of the object; an elevation to 
represent the sides of the body, and to express its height; and a plan 
of the upper surface to express the form horizontally. 

It is to be observed that this body has an imaginary axis or 
center line, about which the same parts or segments of the body 
are equally distant; this is an essential characteristic of all sym- 
metrical figures. 

Draw a horizontal dotted line M N for the center line of the 
plan views, Fig. 130. Then draw a perpendicular ZZ' to M N. 

In delineating the pyramid, it is necessary, in the first place, 
to construct the plan. The point S', where the line ZZ' intersects 
the line M N, is to be taken as the center of the figure, and from 
this point, with a radius equal to the side of the hexagon which 
forms the base of the pyramid, describe a circle, cutting M N in A' 
and D'. From these points, with the same radius, draw four arcs 
of circles, cutting the primary circle in four points. These six points 
being joined by straight lines, will form the figure A' B' C D f E' ' F' ', 



161 






MECHANICAL DRAWING 



which bthe base <rf the pyramid; and the lines A'W, B' E\ and C F\ 
will represent the projections of its edges foreshortened as they 

would, appear in the plan. If this operation has been correctly per- 

ed, the opp es of the hexagon should be parallel to 

h other and to one of the diagonals; this should be tested by 

the application of the square or other instrument proper for the 



purpose. 



By the help of the plan obtained as above described, the vertical 




-N 



3 |6" C D 

Z 

n of Regular Hexagonal Pyramid 

projection of the pyramid may be easily constructed. Since it is 

directly under the plan, it must be projected vertically downward; 
then m each of points A '. />''. C, D', drop perpendiculars 

to AD, i of the pyramid in the elevation. The points 

of in1 ., A, 11. ( , and D, are the true positions of all the 

- J of 1 to determine the height of 

pyramid, which i- to be set off from the point G to S, and to 



162 



MECHANICAL DRAWING 97 

draw SA, SB, S C, and SD, which are the only edges of the pyramid 
visible in the elevation. Of these it is to be remarked that SA 
and SD alone, being parallel to the vertical plane, are seen in their 
true length; and, moreover, that from the assumed position of the 
solid under examination, the points F f and E f being situated in 
the lines BB' and CC f , the lines SB and S C are each the projections 
of two edges of the pyramid. 

2. Construct the projections of the pyramid, Example 1, having 
its base set in an inclined position, but with its edges SA and SD 
still parallel to the vertical plane, Fig. 130. 

It is evident, that with the exception of the inclination, the 
vertical projection of this solid is precisely the same as in the pre- 
ceding example, and it is only necessary to show the same view of 
the pyramid in its new position. For this purpose, after having 
fixed the position of the point D, draw through this point a straight 
line DA, making with M N an angle equal to the desired inclination 
of the base of the pyramid. Then set off the distance DA, equal 
to that used in Example 1; erect a perpendicular on the center, 
and set off GS equal to the height of the pyramid. Transfer also 
from the first example the distance BG and CG to the corresponding 
points, and complete the figure by drawing the straight lines AS, 
BS, CS, srndDS. 

In constructing the plan of the pyramid in this position, it is 
to be remarked that since the edges S A and S D are still parallel 
to the vertical plane, and the point D remains unaltered, the projec- 
tion of the points A, D, and S, will still be in the line M N. The 
position of A ' is determined by the intersection of the perpendicular 
A A' with M N. The remaining points, B ; , C r , etc., in the projec- 
tion of the base, are found, in a similar manner, by the intersections 
raised from the corresponding points in the ekvation, with lines 
drawn parallel to M N, at a distance (set off at o, p) equal to the 
width of the base. By joining all the contiguous points, the figure 
A' B' C' D' E' F' is obtained representing the horizontal projection 
of the base, two of its sides, however, being dotted, as they must 
be supposed to be concealed by the body of the pyramid. The vertex 
S having been similarly projected to S r , and joined by straight 
lines to the several angles of the base, the projection of the solid 
is completed. 



163 



9S 



MECHANICAL DRAWING 



INTERSECTIONS 

If one surface meets another at some angle, an intersection is 
produced. Either surface may be plane, or curved. If both are 
plane, the intersection is a straight line; if one is curved, the inter- 
Mrtion is a curve, except in a few special cases; and if both are 
curved, the intersection is usually curved. In the latter case, the 





Fig. 131. Intersection of Plane 
and Square Pyramid 



Fig. 132. Intersection of Plane 
and Triangular Pyramid 



entire curve does not always lie in the same planes. If all points 
of any curve lie in the same plane, it is called a plane curve. A 
plane intersecting a curved surface must always give either a plane 
curve or a straight line. 

Planes with Planes. In Fig. 131 a square pyramid is cut by a 
plane -1 parallel to the horizontal. This plane cuts from the pyra- 



164 



MECHANICAL DRAWING 



99 



mid a four-sided figure, the four corners of which will be the points 
where A cuts the four slanting edges of the solid. The plane inter- 
sects edge o b at point 4 U in elevation. This point must be found 
in plan vertically above on the horizontal projection of line ob, 
that is, at point 4'\ Edge o e is directly in front of o b, so is shown 
in elevation as the same line, and plane A intersects oe at point Pin 





Fig. 133. Intersection of Plane and Prism 



Fig. 134. Intersection of 
Plane and Cone 



elevation, found in plan at l h . Points 3 and 2 are obtained 
in the same way. The intersection is shown in plan as the square 
1-2-3-4, which is also its true size as it is parallel to the horizontal 
plane. In a similar way the intersections are found in Figs. 132 
and 133. It will be seen that in these three cases where the plen^s 
are parallel to the bases, the sections are of the same shape as the 
bases, and have their sides parallel to the edges of the bases. 



165 






MECHANICAL DRAWING 



It is an invariable rule that when such a solid is 1 cut by a plane 

parallel to its base, the section is a figure of the same shape as the 

If then in Fig. 134 a right cone is intersected by a plane 

parallel to the base the section must be a circle, the center of which 

in plan coincides with the apex. The radius must equal od. 

In Fig. 135 and Fig. 136 the cutting plane is not parallel to the 
base, hence the section will not be of the same shape as the base. 




Fig. 135. Intersection of Plane 
and Square Pyramid 



Fig. 136. Intersection of Plane 
and Hexagonal Pyramid 



The intersections are found, however, in exactly the same manner 
as in the previous figures, by projecting the points where the plane 
intersects the edges in elevation, on to the other view of the 
same line. 

ILLUSTRATIVE EXAMPLES 
1. Find the horizontal projection of a transverse section of 
the pyramid of Pig. 130, made by a plane perpendicular to the 
vertical, but inclined at an angle to the horizontal plane of projec- 
tion; and let all the sides of the base be at an angle with M X, Fig. 137. 



166 



MECHANICAL DRAWING 



101 



Having drawn the vertical SS', the center line of the figures, 
its point of intersection with the line M N is the center of the plan. 
Since none of the sides of the base are to be parallel with M N, draw 
a diameter A'D' making the required angle with M N, and from 
the points A' and D' proceed to set out the angular points of the 
hexagon, as in Fig. 130. Then join the angular points which are 
diametiically opposite and pro- 
ject the figure thus obtained 
upon the vertical plane, as shown. 

Now, if the cutting plane 
be represented by the line ad in 
the elevation, it is obvious that 
it will expose, as the section of 
the pyramid, a polygon whose 
angular points being the inter- 
sections of the various edges 
with the cutting plane, will be 
projected in perpendiculars drawn 
from the points where it meets 
these edges respectively. From 
the points a, /, b, etc., raise the 
perpendiculars a a' ',//', bb f , etc., 
to meet the lines A' D' 9 FC", 
B f E' ', etc. When the contiguous 
points of intersection of these 
lines are joined, a six-sided figure 
will be formed which will repre- 
sent the section required. The 
edges F.S and ES being con- 
cealed in the elevation, but necessary for the construction of the 
plan, have been expressed in dotted lines, as is also the portion of 
the pyramid situated above the cutting plane which, though sup- 
posed to be removed, is necessary in order to draw the lines 
representing the edges. 

2. Find the horizontal projection of the transverse section of a 
regular five-sided pyramid, cut by a plane perpendicular to the 
vertical, but inclined at an angle to the horizontal plane of pro- 
jection; and let one edge of the pyramid, BS, be in a plane 




Fig. 137. Frustum of Hexagonal Pyramid 



167 



102 



MECHANICAL DRAWING 



perpendicular to both the horizontal and the vertical planes of 
projection, as shown in Fig. 138. 

The plan of the pyramid is constructed by describing from the 
center 8* a circle circumscribing the base, and from B f dividing 
the circumference into five equal parts, and joining the contiguous 
points of division by straight lines. These form the polygon 

A' B' C D r E', whose angles, when 
joined to the center S', show the 
projections of the edges of the pyra- 
mid. Then, following the method 
above explained, the elevation and 
the horizontal projection of the 
section made by the plane a c are 
obtained. But that method will 
not suffice for the determination 
of the point b', because the per- 
pendicular let fall from the cor- 
responding point b, in the eleva- 
tion, coincides with the projection 
of the edge B S. Let the pyramid 
supposedly be turned a quarter 
of a revolution round its axis; 
the line B' S f will then have 
assumed the position S r b 2 . Pro- 
ject the point b 2 to b 3 , and join 
S b 3 . Then since the required point 
must also be conceived to have 
described a quarter of a circle in 
a plane parallel to the horizontal 
plane, and that its new position 
must be in the line Sb 3 , it is obvious that its vertical projection is 
the point b\ the intersection of a horizontal line drawn through b 
with tlie line Sb 3 . The distance 66 4 may then be used to determine 
the distance from S' to b', and determines the position of the latter 
point in the plan; or, following a more methodical process, by pro- 
jecting the point b 4 to b r °, and describing a circle from the center 
8' passing through b :> , its intersection with B'S' is the point 
sought. 




/J 

Fig. 138 



E B DC 

Frustum of Pentagonal Pyramid 



168 



MECHANICAL DRAWING 



103 



Planes with Cones or Cylinders. Sections cut by a plane 
from a cone have already been defined as conic sections. These 
sections may be any of the following: two straight lines, circle, 
ellipse, parabola, hyperbola. All except the parabola and hyper- 
bola may also be cut from a cylinder. 

Methods have previously been given for constructing the 
ellipse, parabola, and hyper- 
bola, without projections; 
it will now be shown that 
they may be obtained as 
actual intersections/ 

Ellipse. In Fig. 139 
the plane cuts the cone 
obliquely. To find points 
on the curve in plan take 
a series of horizontal planes 
xyz, etc., between points 
c° and d\ One of these 
planes, as w, should be taken 
through the center of cd. 
The points c and d must be 
points on the curve, since 
the plane cuts the two con- 
tour elements at these 
points. Contour elements 
are those forming the out- 
line. The horizontal pro- 
jections of the contour ele- 
ments will be found in a 
horizontal line passing 
through the center of the base; hence the horizontal projection of 
c and d will be found on this center line, and will be the extreme 
ends of the curve. 

The plane x cuts the surface of the cone in a circle, as it is parallel 
to the base, and the diameter of the circle is the distance between 
the points where x crosses the two contour elements. This circle, 
lettered x on the plan, has its center at the horizontal projection of 
the apex. The circle x and the curve cut by the plane are both on 




Fig. 139. Ellipse — Section from a Cone 



169 



104 



MECHANICAL DRAWING 



the surface of the tone, and their vertical projections intersect at 
the points 2-2. Point 2 on the elevation then represents two points 
which arc shown in plan directly above on the circle x, and are 
points on the required intersection. Planes y and z, and as many 
i in, re as may be necessary to determine the curve accurately, are 
used in the same way. The curve found is an ellipse. The student 
will readily see that the true size of this ellipse is not shown in 

the plan, for the plane containing 
the curve is not parallel to the 
horizontal. 

In order to find the actual size 
of the ellipse, it is necessary to place 
its plane in a position parallel either 
to the vertical or to the horizontal. 
The actual length of the long diam- 
eter of the ellipse must be shown in 
elevation, c v d v , because the line is 
parallel to the vertical plane. The 
plane of the ellipse then may be 
revolved about c v d v as an axis until 
it becomes parallel to V, when its 
true size will be shown. For the sake 
of clearness of construction, c v d v is 
imagined moved over to the posi- 
tion c r d' , parallel to c v d v . The lines 
1-1, 2-2, 3-3 on the plan show the 
true width of the ellipse, as these 
lines are parallel to H, but are pro- 
jected closer together than their 
actual distances. In elevation these 
lines are shown as the points 1, 2, 3, 
at their true distance apart. Hence if the ellipse is revolved 
around iis axis c'd ', the distances 1-1, 2-2, 3-3 may be laid off on 
lines perpendicular to c v d°, and the true size of the figure be shown. 
In Fig. 1 10 a plane cuts a cylinder obliquely. This is a simpler 
ilic horizontal projection of the curve coincides with the 
base of the cylinder. To obtain the true size of the section, which 
! ellipsei any number of points are assumed on the plan and 




Fig. 140. Ellipse -Section from a 
Cylinder 



170 



MECHANICAL DRAWING 



105 



projected down on the cutting plane, at 1, 2, 3, etc. The lines drawn 
through these points perpendicular to 1/-7' are made equal in length 
to the corresponding distances 2'-2', 3'-3', etc., on the plan, because 
2'-2' is the true width of curve at 2. 

Parabola. If a cone is intersected by a plane which is parallel 
to only one of the elements, as in Fig. 141, the resulting curve is 




Fig. 141. Parabola — Section from a Cone 

the parabola, the construction of which is exactly similar to that for 
the ellipse, as given in Fig. 139. If the intersecting plane is parallel 
to more than one element, or is parallel to the axis of the cone, a 
hyperbola is produced. 

In Fig. 142, the vertical plane A is parallel to the axis of the 
cone. In this instance the curve when found will appear in its true 



171 






MECHANICAL DRAWING 



lane - 1 is parallel to the vertical. Observe that the highest 
point of the curve is found by drawing the circle X on the plan 

tangent to the given plane. 
One of the points where 
this circle crosses the diam- 
eter is projected down to 
the contour element of the 
cone, and the horizontal 
plane X drawn. Interme- 
diate planes Y, Z, etc., are 
chosen, and corresponding 
circles drawn in plan. The 
points where these circles 
are crossed by the plane .1 
are points on the curve, 
and these points are pro- 
jected down to the eleva- 
tion on the planes Y, Z, etc. 

DEVELOPMENT OF 
SURFACES 

General Details of 
Process. A surface may 
be considered as formed by 
the motion of a line. Any 
length of line moved side- 
wise in any direction will 
form a surface, of a width 
equal to the length of the 
line, and of a length equal 
to the distance over which 
the line is moved. There 
are two different classes 
of surfaces; namely, those 
formed by a moving 

Straight line, and those formed by a moving curved line. 

In some construction work, patterns of different face- or of 

the whole surface must be made; in stone cutting, for example, 




-'. Hyperbola— Section from a Cone 



172 



MECHANICAL DRAWING 



107 



there must be a pattern giving the shape of any irregular surface, 
and in sheet-metal work a pattern must be made such that, when a 
sheet is cut, it can be so formed that it will be of the same shape 
as the original object. 

This pattern making, or the laying out of a complete surface 
on one plane, is called the development of the surface. Any surface 




Fig. 143. Development of a Right Cylinder Rolled Out on a Plane 

which can be smoothly wrapped about by a sheet of paper, can be 
developed. Figures made up of planes and single curved surfaces 
only would be of this nature. Double curved surfaces and warped 
surfaces cannot be developed, and patterns of such surfaces, when 
desired, must be made by an approximate method which requires 
two or more pieces to make the complete pattern. 




Fig. 144. Development of a Right Cone Rolled Out on a Plane 

By finding the true size of all the faces of an object made up 
of planes, and joining them in order at their common edges, the 
developed surface will be formed. The best way to do this is to 
find the true length of the edges of the object. 

Right Cylinder. In Fig. 143 is represented a right cylinder 
rolling on a plane. The development is formed by one complete 



173 






MECHANICAL DRAWING 



revolution of the cylinder and is a rectangle, the width being equal 
to the height of the cylinder and the length to the circumference. 

Right Cone. In Fig. 144 is represented a right cone rolling 
out its development, which is a sector of a circle. The arc equals 
the circumference of the circle forming the base of the cone, and 
the radius equals the slant height. 

The projections of any object must be drawn before the develop- 
ment can be made, but it is necessary only to draw such views as 
arc required for finding the lengths of elements, and true sizes of 
eut surfaces. 

Rectangular Prism. In order to find the development of the 
rectangular prism in Fig. 145, the back face, 1-2-7-6, is supposed 




/ 



5 8 

Fig. 145. Development of Hollow Rectangular Prism 



to be placed in contact with some plane, then the prism turned 
on the edge 2-7 until the side 2-3-8-7 is in contact with the same 
plane, and this process continued until all four faces have been placed 
on the same plane. The rectangles 1-2-3-4 and 6-7-8-5 are for the 
top and bottom, respectively. The development then is the exact 
size and shape of a covering for the prism. If a rectangular hole 
is cut through the prism, the openings in the front and back faces 
will be shown in the development in the centers of the two broad 



174 



MECHANICAL DRAWING 



109 



The development of a right prism, then, consists of as many 
rectangles joined together as the prism has sides, these rectangles 
being the exact size of the faces of the prism, and in addition two 
polygons the exact size of the bases. It will be found helpful in 
developing a solid to number or letter all of the corners on the 
projections, then designate each face when developed in the same 
way as in the figure. 

Cone. If a cone be placed on its side on a plane surface, one 
element will rest on the surface. If now the cone be rolled on the 





Fig. 146. Plan and Elevation 
of Cone 



Fig. 147. Development of Cone 



plane, the vertex remaining stationary until the same element is 
in contact again, the space rolled over will represent the develop- 
ment of the convex surface of the cone. Fig. 146 is a cone cut by 
a plane parallel to the base. In Fig. 147, let the vertex of the cone 
be placed at V, and one element of the cone coincide with VF1. 
The length of this element is taken from the elevation, Fig. 146, 
of either contour element. All of the elements of the cone are of 
the same length, so that when the cone is rolled, each point of the 
base as it touches the plane will be at the same distance from the 
vertex. From this it follows that in the development of the base, 



175 



lit) 



MECHANICAL DRAWING 



the circumference will become the arc of a circle of radius equal 
to the length of an element, and of a length equal to the distance 
around the base. To find this length divide the circumference 
of the base in the plan into any number of equal parts, say twelve, 
and lay off twelve such spaces, 1 .... 13 along an arc drawn with 
radius equal to VI; join 1 and 13 with V, and the resulting sector 
is the development of the cone from vertex to base. In order to 
represent on the development the circle cut by the section plane DF, 
draw, from the vertex V as a center and with VF as a radius, the 

arc F C. The development of the frus- 
tum of the cone will be a portion of a 
circular ring. This of course does not 
include the development of the bases, 
which would be simply two circles the 
same sizes as shown in plan. 




Plan and El< 

of Triangular Pyramid 




Fig. 149. Development of Triangular Pyramid 



Regular Triangular Pyramid. Fig. 148 represents the plan and 
elevation of a regular triangular pyramid, and Fig. 149 its develop- 
ment, [f face C is placed on the plane its true size will be shown 
in the development. The true length of the base of triangle C is 
shown in the plan. As the slanting edges, however, are not parallel 
to the vertical, their true length is not shown in elevation but must 
be obtained by the method given on page 88, as indicated in Fig. 148. 
The triangle may now be drawn in its full size at C in the develop- 
ment, and as the pyramid is regular, two other equal triangles, 



176 



MECHANICAL DRAWING 



111 



D and E, may be drawn to represent the other sides. These, together 
with the base F, constitute the complete development. 

Truncated Circular Cylinder. If a truncated circular cylinder 
is to be developed, or rolled upon a plane, the elements, being 
parallel, will appear as parallel lines, and the base line being per- 
pendicular to the elements, will appear as a straight line of length 
equal to the circumference of the base. The base of the cylinder 
in Fig. 150 is divided into twelve equal parts, 1, 2, 3, etc., and com- 
mencing at point 1 on the development, these twelve equal spaces 
are laid off along the straight line, giving the total width. 




/£ // /<? 9 8 J 6 5 4 3 

Fig. 150. Projections and Development of Truncated Cylinder 

Draw in elevation the elements corresponding to the various 
divisions of the base, and note the points where they intersect the 
oblique plane. As the cylinder is rolled beginning at point 1, the 
successive elements, 1, 12, 11, etc., will appear at equal distances 
apart, and equal in length to the lengths of the same elements in 
elevation. Thus point number 10 on the development is found by 
projecting horizontally across from 10 in elevation. It will be seen 
that the curve formed is symmetrical, the half on the left of 7 being 
similar to that on the right. The development of any similar surface 
may be found in the same manner. 

The principle of cylinder development is used in laying out 
elbow joints, pipe ends cut off obliquely, etc. In Fig. 151 is shown 



177 






MECHANICAL DRAWING 



plan and elevation of a three-piece elbow and collar, and develop- 
ments of the four pieces. In order to construct the various parts 
making up the joint, it is necessary to know what shape and size 
must he marked out on the flat sheet metal so that when cut out 
and rolled up the three pieces will form cylinders with the ends 
fitting together as required. Knowing the kind of elbow desired, 
first draw the plan and elevation, and from these make the develop- 




Fig. 151. Plan, Elevation, and Development of Three-Piece Elbow and Collar 

ments. Let the lengths of the three pieces A, B, and C be the same 
on the upper outside contour of the elbow, the piece B at an angle 
of 4o degrees; the joint between A and B bisects the angle between 
the two lengths, and in the same way the joint between B and C. 
The lengths A and C will then be the same and one pattern will 
answer for both. The development of .1 is made exactly as just 
explained for Fig. 150, and this is also the development of C. 

It should be borne in mind that in developing a cylinder the 
l>;i-e must always be at right angles to the elements, and if the 
cylinder as given does not have such a base, it becomes necessary 



178 



MECHANICAL DRAWING 113 

to cut the cylinder by a plane perpendicular to the elements, and 
use the intersection as a base. This point must be clearly under- 
stood in order to proceed intelligently. A section at right angles 
to the elements is the only section which will unroll in a straight 
line, and is, therefore, the section from which the other sections 
must be developed. As B, Fig. 151, has neither end at right angles 
to its length, the plane X is drawn at the middle and perpendicular 
to the length. B has the same diameter as C and A, so the section 
cut by X will be a circle of the same diameter as the base of A, 
and is shown in the development at X. 

The elements on B are drawn from the points where the elements 
on the elevation of A meet the joint between A and B, and are equally 
spaced as shown on the plan of A. Commencing with the left- 
hand element in B, the length of the upper element between X 
and the top corner of the elbow is laid off above X, giving the first 
point in the development of the end of B fitting with C. The lengths 
of the other elements in the elevation of B are measured in the 
same way and laid off from X. The development of the other 
end of the piece B is laid off below X, using the same distances, 
since X is half way between the ends. The development of the 
collar is simply the development of the frustum of a cone, which 
has already been explained, Fig. 147. The joint between B and 
C is shown in plan as an ellipse, the construction of which the student 
should be able to understand from a study of the figure. 

ISOMETRIC PROJECTION 

Isometric of a Cube. In orthographic projection an object 
has been represented by two or more projections; another system, 
called isometrical drawing, is often used to show in one view the three 
dimensions of an object, length (or height), breadth, and thickness. 
An isometrical drawing of an object, as a cube, is called for brevity 
the isometric of the cube. 

To obtain a view which shows the three dimensions in such a 
way that measurements may be taken from them, draw the cube in 
the simple position shown at the left, Fig. 152, with two faces parallel 
to V; the diagonal from the front upper right-hand corner to the back 
lower left-hand corner is indicated by the dotted line. Swing the 
cube around until the diagonal is parallel with V, as shown in the 



179 






MECHANICAL DRAWING 



,1 position. Here the front face is at the right. In the third 
position the lower end of the diagonal has been raised so that it is 
parallel to II, becoming thus parallel to both planes. The plan 
is found by the principles of projection, from the elevation and the 
preceding plan. The front face is now the lower of the two faces 
shown in the elevation. From this position the cube is swung around, 
using the corner as a pivot, until the diagonal is perpendicular to 
I' but -till parallel to //. The plan remains the same, except as 

rda position; while the elevation, obtained by projecting across 
from the previous elevation, gives the isometrical projection of the 
cube. The front face is now at the left. 

Distinction between Isometric Projection and Isometric Drawing. 
In the last position, as one diagonal is perpendicular to V, it follows 




Fig. 152. Development of an Isometric of a Cube 

that all the faces of the cube make equal angles with V, hence 
arc projected on that plane as equal parallelograms. For the same 
reason all the edges of the cube are projected in elevation in equal 
lengths, but, being inclined to V, appear shorter than they actually 
arc on the object. Since they are all equally foreshortened and since 
a drawing may be made at any scale, it is customary to make all the 
isometrical lines of a drawing full length. This will give the same 
proportions, and is much the simpler method. Herein lies the dis- 
tinction between an isometric projection and an isometric drawing. 
It will be noticed that the figure may be inscribed in a circle, 
i hat the outline is a perfect hexagon. Hence the lines showing 



180 



MECHANICAL DRAWING 



115 



breadth and length are 30-degree lines, while those showing height 
are vertical. 

True Length of Lines. Fig. 153 shows the isometric of a cube 
1 inch square. All of the edges are shown in their true length, hence 





Fig. 153. Isometric of a Cube 



Fig. 154. Plan and Ele- 
vation of a Cube 



all the surfaces appear of the same size. 
In the figure the edges of the base are 
inclined at 30 degrees with a T-square 
line, but this is not always the case. For 
rectangular objects, such as prisms, cubes, 
etc., the base edges are at 30 degrees 
only when the prism or cube is sup- 
posed to be in the simplest possible 
position. The cube in Fig. 153 is sup- 
posed to be in the position indicated by 
plan and elevation in Fig. 154, that is, 
standing on its base, w T ith two faces 
parallel to the vertical plane. 

If the isometric of the cube in the 
position shown in Fig. 155 were required, 
it could not be drawn with the base 
edges at 30 degrees; neither would these 
edges appear in their true lengths. It 



1 1 









Fig. 155. Cube of Fig. 154 Rotated 
30 Degrees with Vertical Plane 



181 






MECHANICAL DRAWING 







ric of a Cube with Circles 
Inscribed on its Faces 



follows, then, that in isometrical drawing, true lengths appear 
only as 30-degree lines or as vertical lines. Edges or lines that in 

actual projection are either 
parallel to a T-square line or 
perpendicular to V, are drawn 
in isometric as 30-degree lines, 
full length; and those that are 
actually vertical are made 
vertical in isometric, also full 
length. 

Three Isometric Axes. In 
Fig. 152, lines such as the 
front vertical edges of the 
cube and the two base edges 
are called the three isometric 
axes. The isometric of objects 
in oblique positions, as in 
Fig. 155, can be constructed 
only by reference to their projections, by methods which will be 
explained in the section on "Oblique Projection", page 123. 

Applications of Isometric Pro- 
^/V^ jections. In isometric drawing 

small rectangular objects are more 
satisfactorily represented than 
\ { ,J*\ large curved ones. In woodwork, 
mortises and joints and various 
parts of framing are well shown 
in isometric. This system is used 
also to give a kind of bird's-eye 
view of mills or factories. It is also 
used in making sketches of small 
rectangular pieces of machinery, 
where it is desirable to give shape 
and dimensions in one view. 

Characteristics of Various 
Isometrics. Cube with Inscribed 
Circles. V\z. 156 shows a cube with circles inscribed in the top 
and two side faces. The isometric of a circle is an ellipse- the 




y 






Isometric of a Cylinder 



182 



MECHANICAL DRAWING 



117 



exact construction of which would necessitate finding a number 
of points; for this reason an approximate construction by arcs of 
circles is often made. In the method, Fig. 156, four centers are 
used. Considering the upper face of the cube, lines are drawn 
from the obtuse angles / and e to the centers of the opposite sides. 
The intersections of these lines give points g and h, which serve 
as centers for the ends of the ellipse. With g as center and radius 
ga y the arc ad is drawn, and with/ as center and radius fd, the arc 





Fig. 158. Isometric of a Wooden 
Block 



Fig. 159. Isometric of a Wooden 
Brace 



dc is drawn; the ellipse is finished by using centers h and e. This 
construction is applied to all three faces. 

Cylinder, Fig. 157 is the isometric of a cylinder standing 
on its base. 

Blocks. Fig. 158 represents a block with smaller blocks pro- 
jecting from three faces. 

Frameicork. Fig. 159 shows a framework of three pieces, 
two at right angles and a slanting brace. The horizontal piece is 
mortised into the upright as indicated by the dotted lines. 

House. In Fig'. 160 the isometric outline of a house is repre- 
sented, showing a dormer window and a partial hip roof; at is a hip 
rafter, c d a valley. Let the pitch of the main roof be shown at B, 
and let m be the middle point of the top of the end wall of the house. 
Then, by measuring vertically up a distance m I equal to the vertical 



183 



MECHANICAL DRAWING 

_,t a n shown at 11. a point on the line of the ridge will be found 
at /. line I i is equal to bh, and ih is then drawn. Let the pitch 
of the end roof be given at A. This shows that the peak of the roof, 
or the end a of the ridge, will be back from the end wall a distance 
equal to the base of the triangle at A. Hence, lay off from I this 
distance, giving point a, and join a with b and x. 

The height ke of the ridge of the dormer roof is known, and it 
must be found where this ridge will meet the main roof. The ridge 
musl be a 30-degree line as it runs parallel to the end wall of the house 
and to the ground. Draw from e a line parallel to b h to meet a 
vertical through h and /. This point is in the vertical plane of 




B 



*d' 



Fig. 160. Isometric Outline of a House 



the end wall of the house, hence in the plane of ih. If now a 30- 
degree line be drawn from/ parallel to x b, it will meet the roof of 
the house at g. The dormer ridge smdfg are in the same horizontal 
plane, hence will meet the roof at the same distance below the ridge 
at. Therefore draw the 30-degree line gc, and connect c with d. 

Box with Cover. In Fig. 161 a box is shown with the cover 
opened through 150 degrees. The right-hand edge of the bottom 
shows the w -idth, the left-hand edge shows the length and the vertical 
shows the height. The short edges of the cover are not 
isometric lines, hence are not shown in their true lengths; neither 
is the angle through which the cover is opened represented in its 
actual size. 



184 



MECHANICAL DRAWING 



119 



The corners of the cover must then be determined by co-ordinates 
from an end view of the box and cover. As the end of the cover 






Fig. 161. Isometric of a Box and Cover 

is in the same plane as the end of the box, the simple end view as 
shown in Fig. 162 will be sufficient. Extend the top of the box to 
the right, and from c and d 
let fall perpendiculars on 
a b produced, giving the 
points e and /. The point 
c may be located by means 
of the two distances or co- 
ordinates be and ec, and 
these distances will appear 
in their true lengths in the 
isometric view. Hence pro- 
duce a' V to e' and f ; and 
from these points draw ver- 
ticals e' c' and fd f ; make V V equal to be, e' V equal to ec; and simi- 
larly for d'. Draw the lower edge parallel to c' ' d' and equal to it 
in length, and connect with b' '. 



Fig. 162. End View of Box Shown in Fig. 161 



185 






MECHANICAL DRAWING 



It will be seen that in isometric drawing parallel lines always 
ear parallel. It is also true that lines divided proportionally 
maintain this same relation in isometric drawing. 

P r i s m with Sem icircula r 
Top. Fig. 163 shows a block or 
prism with a semicircular top. 
Find the isometric of the square 
circumscribing the circle, then 
draw the curve by the approxi- 
mate method. The centers for 




Fig. 1<">3. Isometric of a Prism 
with Semicircular Top 




c- .V 



• 




Plan and Elevation of 
Oblique Pentagonal Pyramid 



the l»;uk face are found by projecting the front centers back 30 
equal to the thickness of the prism, as shown at a and b. 

Pyramid. The plan and elevation of an oblique pentagonal 
hown in Fig. 104. It is evident that none of the edges 



186 



MECHANICAL DRAWING 



121 




Fig. 166. Isometric of a Skeleton of a Box 



of the pyramid can be drawn in isometric as either vertical or 30- 
degree lines; hence a system of co-ordinates must be used as shown 
in Fig. 165. This problem illus- 
trates the most general case; 
and to locate some of the 
points three co-ordinates must 
be used, two at 30 degrees 
and one vertical. 

Circumscribe, about the 
plan of the pyramid, a rectan- 
gle which shall have its sides 
respectively parallel and per- 
pendicular to a T-square line. 

The isometric of this 
rectangle can be drawn at 
once with 30-degree lines, as 
shown in Fig. 165, o being 
the same point in both figures. The horizontal projection of point 
3 is found in isometric at 3^, at the same distance from o as in the 
plan. That is, any dis- 
tance which in plan is 
parallel to a side of the 
circumscribing rectangle, 
is shown in isometric in 
its true length and par- 
allel to the corresponding 
side of the isometric rec- 
tangle. If point 3 were 
on the horizontal plane 
its isometric would be 3\ 
but the point is at the 
vertical height above H 
given in the elevation; 
hence, lay off above 3 71 
this vertical height, 
obtaining the actual isometric of the point. To locate point 4, 
draw 4a parallel to the side of the rectangle; then lay off. oa 
and a 4\ giving what may be called the isometric plan of 4. The 




Fig. 167. Isometric of a Carpenter's Bench 



187 



12: 



MECHANICAL DRAWING 



vertical height taken from the elevation locates the isometric 
of the point. 




8. Plan and Elevation of 
Sawfa 



Fig. 169. Isometric of Fig. 16S 






In like manner all the corners of the pyramid, including the 
apex, are located. The rule is, locate first in isometric the horizontal 



1 Eleva- 

■ 3 




Fig. 171. Isometric of Stairs 



projection of a point by one or two 'MUder/rce co-ordinates; then ver- 
Hcally above this point, locate its height as taken from the deration. 

■ L66to 173 give examples of the isometric of various objects. 



188 



MECHANICAL DRAWING 



123 



Fig. 168 is the plan and elevation, and Fig. 169 the isometric, of a 
carpenter's sawhorse. 




Fig. 172. Isometric of a Hollow Cylinder Fig. 173. Isometric of a Wooden Model 



OBLIQUE PROJECTION 

Comparison with Isometric Projection. In oblique projec- 
tion, as in isometric, the end sought for is the same — a more or 
less complete representation, in one view, of any object. Oblique 
projection differs from isometric in that one face of the object is 
represented as if parallel to the vertical plane of projection, the 
others inclined to it. Another point of difference is that oblique 
projection cannot be deduced from 
orthographic projection, as is iso- 
metric. 

Characteristics of Method. In 
oblique projection all lines in the 
front face are shown in their true 
lengths and in their true relation to 
one another, and lines which are per- 
pendicular to this front face are 
shown in their true lengths at any 
angle that may be desired for any particular case. Lines not in the 
plane of the front face nor perpendicular to it must be determined by 
co-ordinates, as in isometric. It will be seen at once that this system 




Fig. 174. 



Oblique View of Cube at 30 
Degrees 



189 



124 



MECHANICAL DRAWING 



poss me advantages over the isometric, as, for instance, in the 

itation of circles, as any circle or curve in the front face is 

actually dnr .. Fig. 174, Fig. 175, and Fig. 176 show a cube 

in oblique projection with the 30-degree, 45-degree, and 60-degree 

slant, respectively. Fig. 177 shows 
a hollow cylinder in oblique pro- 
jection. Figs 178, 179, 180, 182 
are other examples of oblique pro- 
jections. Fig. ISO is a crank arm. 
The method of using co-ordi- 
nates for lines of which the true 
lengths are not shown, is illustrated 
by Figs 181 and 182. Fig. 1S2 
represents the oblique projection of 
the two joists shown in plan and 
elevation in Fig. 181. The dotted 
lines in the elevation, Fig. 181, show the heights of the corners 
above the horizontal stick. The feet of these perpendiculars give 
the horizontal distances of the top corners from the end of the 
horizontal piece. 

In Fig. 1S2 lay off from the upper right-hand corner of the front 
end a distance equal to the distance between the front edge of the 




Oblique View of Cube at 45 
Degrees 








l 



Fig. 177. Oblique View of Hollow Cylinder 



inclined piece and the front edge of the bottom piece, Fig. 181. 
From this point draw a dotted line parallel to the length. The 
horizontal distances from the upper left corner to the dotted perpen- 
dicular are then marked off on this line. From these points verticals 



190 



MECHANICAL DRAWING 



125 



are drawn, and made equal in length to the dotted perpendiculars 
of Fig. 181, thus locating two corners of the end. 




Fig. 178. Oblique View of a Miter Joint 




Fig. 179. Oblique View of Cylinder 




Fig. 180. Oblique View of Crank Shaft 





Fig. 181. Plan and Elevation of 
Wooden Brace 



Fig. 182. Oblique View of Wooden 
Brace 



191 



12G 



MECHANICAL DRAWING 




LINE SHADING 

Object of Line Shading. In finely finished drawings it is fre- 
quently desirable to make the various parts more readily seen by 
showing the graduations of light and shade on the 
curved surfaces. This is especially true of such sur- 
faces as cylinders, cones, and spheres. The effect is 
obtained by drawing a series of parallel or converg- 
ing lines on the surface at varying distances from 
one another. Sometimes draftsmen, themselves, 
vary the width of the lines. These lines are 
farther apart on the lighter portion of the sur- 
face, and closer together and heavier on the darker 
part. 

Fig. 183 shows a cylinder with elements drawn 
on the surface equally spaced on the plan. On 
account of the curvature of the surface, however, 
the elements are not equally spaced on the eleva- 
tion, in order to give the effect of the graduations of 
light on the curved surface. The result is that 
in drawing the elevation of the cylinder, the dis- 
tances between the elements are made gradually less from the center 
toward each side, thus giving a correct representation of the con- 
vexity of the cylinder. This effect is intensified by making the 



Fig. \<i. Plan and 
Shaded Elevation 
iinder 








Shaded 
\ ertical ( lylinder 



Fig In.",. Shaded Horizontal 
Cylinder 



Fig. 1S6. Shaded Section 
of Hollow Cylinder 



outside elements heavier as well as closer together, as shown in 
Is I to L90. Concavity is shown in the same manner, the 



192 



MECHANICAL DRAWING 



127 



heavy shading always appearing on the left to indicate the deeper 
shadow, Figs. 186 and 188. 

Fig. 184 is a cylinder showing the heaviest shade at the right, 
a method often used. Considerable practice is necessary to obtain 
good results; but in this, as in other portions of mechanical drawing, 
repetition is unavoidable. Fig. 185 represents a cylinder in a hori- 




Fig. 187. Shaded Elbow Joint 



Fig. 188. Shaded Section of Hollow Sphere 



zontal position, and Fig. 186 represents a section of a hollow vertical 
cylinder. Figs. 187 to 190 give other examples of familiar objects. 





Fig. 189. Shaded Sphere 



Fig. 190. Shaded Cone 



In the elevation of the cone shown in Fig. 190 the shade lines 
should diminish in weight as they approach the apex. Unless this is 
done it will be difficult to avoid the formation of a blot at that point. 



193 



MECHANICAL DRAWING 
LETTERING 

Types of Lettering. In the early part of this course, the inclined 
Gothic letter was described, and the alphabet given. The Roman, 
Gothic, and block letters are perhaps the most used for titles. These 
letters, being of comparatively large size, are generally made 
mechanically; that is, drawing instruments are used in their con- 
struction. In order that the letters may appear of the same height, 
some of them, owing to their shape, must be made a little higher 
than the others. This is the case with the letters curved at the top 
and bottom, such as C, O, S, etc., as shown somewhat exaggerated 
in Fig. 191. Also, the letter A should extend a little above, and V 
a little below, the guide lines, because if made of the same height 
aa the others they will appear shorter. This is true of all capitals, 
whether of Roman, Gothic, or other alphabets. In the block letter, 
however, they are frequently all of the same size. 

Size of Letters. There is no absolute size or proportion of 
letter-, as the dimensions are regulated by the amount of space 
in which the letters are to be placed, the size of the drawing, the effect 
desired, etc. In some cases letters are made so that the height 
is greater than the width, and sometimes the reverse; sometimes 
the height and width are the same. This last proportion is the 
most common. Certain relations of width, however, should be 
observed. Thus, in whatever style of alphabet used, the W should 
be the widest letter; J the narrowest, M and T the next widest 
to W, then A and B. The other letters are of about the same width. 

I - rtical Gothic. In the vertical Gothic alphabet, the average 
height is that of B, D, E, F, etc., and the additional height of the 
curved letters and of the A and V is very slight. The horizontal 
cross lines of such letters as E, F, H, etc., are slightly above the 
center; those of A, G, and P slightly below. 

Inclined Gothic For the inclined letters, Fig. 192, 60 degrees 
i- a convenient angle, although they may be at any other angle 
suited to the convenience or fancy of the draftsman. Many drafts- 
men use an angle of about 70 degrees. 

Unman. The letters of the Roman alphabet, whether vertical, 

193, or inclined, Fig. I'M, are quite ornamental in effect if well 
made, the inclined Roman being a particularly attractive letter. 



194 



MECHANICAL DRAWING 



129 



m 

u 
M 

i i '; 

A 
n ii 

w 

ILlJ! 

M 

M 



IN 

i.V i 



Hi 



I II 




D 

i 1 H 

• ii 

ih 




if**' #11 
1 » 

m 

n !< 



inioo 

N 

. it 





IV^^ii 

QJ 

'I '« 

Jl 




1 " 

Ft 



|| M 



!i '' 3 



s 



IP r o 



a u ii 



| 5j 



S? 

5! 



195 



130 



MECHANICAL DRAWING 




196 



MECHANICAL DRAWING 



131 



although rather difficult to make. The block letter, Fig. 195, is 
made on the same general plan as the Gothic, but much heavier. 
Small squares are taken as the unit of measurement, as shown. 
The use of this letter is not advocated for general work, although 





in m W " ib 



Fig. 195. Block Letters 



if made merely in outline the effect is pleasing. The styles of 
numbers, corresponding with the alphabets of capitals given here, 
are also inserted. When a fraction, such as 2f is to be made, the 
proportion should be about as shown. For small letters, usually 

abcdefghijklmn 
opqrstuvwxyz 

Fig. 196. Vertical Gothic Lower-Case Letters 

called lower-case letters, the height may be made about two-thirds 
that of the capitals. This proportion, however, varies in special 
cases. 

Lower-Case Letters. The principal lower-case letters in general 
use among draftsmen are shown in Figs. 196, 197, 198, and 199. 



197 



MECHANICAL DRAWING 

The Gothic letters shown in Figs 196 and 197 are much easier to 
make than the Roman letters in Figs. 198 and 199. These letters, 

obco/efgh/jk/mn 
opqrs tuvwxjsz 

Fig. 197. Inclined Gothic Lower-Case Letters 

however, do not give as finished an appearance as the Roman. As 
has already been stated in Mechanical Drawing, Part I, the inclined 
letter is easier to make because slight errors are not so apparent. 

abcdefghijklmn 

opqrstuvwxyz 



Fig. 198. Vertical Roman Lower-Case Letters 



Spacing. One of the most important points to be remembered 
in lettering is the spacing. If the letters are finely executed but 

a be defgh ijklmn 
op qrstuvwxyz^ 

Fig. 199. Inclined Roman Lower-Case Letters 

poorly spaced, the effect is not good. To space letters correctly 
and rapidly requires considerable experience; and rules are of little 

TECHNICALITY 

"i. Sample of Letter Spacing 

value on accounl of the many combinations in which letters are 
found. A few direction-, however, may be found helpful. For 



198 



MECHANICAL DRAWING 133 

instance, take the word TECHNICALITY, Fig. 200. If all the 
spaces were made equal, the space between the L and the I would 
appear to be too great, and the same would apply to the space 
between the I and the T. The space between the H and the N 
and that between the N and the I would be insufficient. Usually, 
when the vertical side of one letter is followed by the vertical side 
of another, as in H E, H B, I R, etc., the maximum space should 
be allowed. Where T and A come together the least space is given, 
for in this case the top of the T frequently extends over the bottom 
of the A. In general, the spacing should be such that a uniform 
appearance is obtained. For the distances between words in a 
sentence, a space of about 1J the width of the average letter may 
be used. The space, however, depends largely upon the desired 
effect. 

Penciling before Inking. For large titles, such as those placed 
on charts, maps, and some large working drawings, the letters 
should be penciled before inking. If the height is made equal to 
the width, considerable time and labor will be saved in laying out 
the work. This is especially true with such Gothic letters as O, 
Q, C, etc., as these letters may then be made with compasses. If 
the letters are of sufficient size, the outlines may be drawn with the 
ruling pen or compasses, and the spaces between filled in with a 
fine brush. 

Titles for Working Drawings. The titles for working drawings 
are generally placed in the lower right-hand corner. Usually a 
draftsman has his choice of letters, mainly because after he has 
become used to making one style he can do it rapidly and accurately. 
However, in some drafting rooms the head draftsman decides what 
lettering should be used. In making these titles, the different 
alphabets are selected to give the best results without spending 
too much time. In most work the letters are made in straight 
lines, although frequently a portion of the title is found lettered 
on an arc of a circle. 

In Fig. 201 is shown a title having the words CONNECTING 
ROD lettered on an arc of a circle. To do this work requires con- 
siderable patience and practice. First, draw the vertical center 
line as shown at C in Fig. 201, then, draw horizontal lines for the 
horizontal letters. The radii of the arcs depend upon the general 



199 



MECHANICAL DRAWING 

arrangement of the entire title, and this is a matter of taste. The 
difference between the arcs should equal the height of the letters. 
After the arc is drawn, the letters should be sketched in pencil to 
Snd their approximate positions. After this is done, draw radial 
lines from the center of the letters to the center of the arcs. These 




' V^ FOR "V N 

BEAM ENGINE 

Fig. 201. Sample Title 

lines will be the centers of the letters, as shown at A, B, D, and E. 
The vertical lines of the letters should not radiate from the center 
of tin* arc, but should be parallel to the center lines already drawn; 
otherwise the letters will appear distorted. Thus, in the letter N 

SAFETY STOP VALVE 

Fig. 202. Sample Title 

the two verticals are parallel to the line A. The same applies to 
the other letters in the alphabet. In making the curved letters 
such as O and C, the centers of the arcs will fall upon these center 
lines; and if the compasses are used, the lettering is a comparatively 
simple matter. In Fig. 202 is shown another title in which all the 
letters are in horizontal lines. 

PLATES 

Plates IX to XV, inclusive, are to be drawn by the student 
for ] tract ice in applying the principles of orthographic projection, 
intersections and developments, isometric and oblique projection, 
and tor practice in lettering. These plates are to be made 11 inches 
by 15 indies outside, with a margin of \ inch, making the clear 

e for the drawing ]() inches by 14 inches. All the plates are 
inked. 



200 



MECHANICAL DRAWING 135 

PLATE IX 

After laying out the border line on the plate, draw a ground 
line horizontally across the upper part of the plate, 3 inches below 
the upper border line. On this ground line six figures, spaced as 
regularly as possible, are to be drawn, as follows: 

1. Draw the projections of a line 1J inches long which is 
parallel to both planes, 1 inch above the horizontal, and f inch 
from the vertical. 

2. Draw the plan and elevation of a line \\ inches long which 
is perpendicular to the horizontal plane and 1 inch from the vertical. 
Lower end of line is \ inch above H. 

3. Draw the projections of two intersecting lines: one 2 inches 
long to be parallel to both planes, 1 inch above H, and f inch from 
the vertical; and the other to be oblique to both planes and of any 
desired length. 

Note. The idea for drawing the three figures referred to in 1, 2, and 3 can 
be obtained from Figs. 104 and 105 in this textbook. 

4. Find the true length of a line whose vertical projection is 
\\ inches long, the left end on the ground line and inclined at 30 
degrees. The horizontal projection has the left end \ inch from 
V, and the right 1J inches from V. 

5. Find the true length of a line whose horizontal projection 
is 1 inch long, whose right end is f inch above the ground line, and 
inclined at 60 degrees. The vertical projection has the right end 
\ inch below the ground line and the left 1 inch. 

6. Find the true length of a line whose projections are per- 
pendicular to the ground line. The horizontal projection is 2 inches 
long, the bottom end being \ inch above the ground line. The 
vertical projection is 1 inch long, the top end being \ inch below 
the ground line. 

Note. The idea for drawing the figures referred to in 4, 5, and 6 can be 
obtained from Figs. 120 and 121 in this textbook. 

In the lower half of the plate, four more figures are to be drawn, 
also spaced as regularly as possible, so that the finished plate will 
be well balanced: 

7. Draw the plan and elevation of a round bolt with a square 
head. The head is to be uppermost- in the elevation. The bolt 



201 



MECHANICAL DRAWING 

is to be 2 inches long and § inch in diameter. The head is to be 
J inch square, J inch thick, and have one face parallel to V. 

8. Draw the plan and elevation of a round bolt having the 
same dimensions as in 7, but with a hexagonal head; the head to 
be uppermost in the elevation, and to be J inch in width between 

3 J inch thick, and to have one face parallel to V. 

9. Draw the plan and elevation of a cylinder, perpendicular 
to //, 2 inches high and 2 inches in diameter, with a hole 1 inch 
in diameter passing vertically completely through it. 

10. Draw the plan, elevation, and end view of a rectangular 
block 6 inches long, 2 inches wide, and 1 inch thick. One of the 
2 inch by inch sides is to be parallel to //. The right end is turned 
down to a cylindrical form 1 inch in length and 1 inch in diameter. 

In all the work of this plate, construction lines should be fine 
dotted lint'- and should be inked in. 

PLATE X 

The figures on the reproduced Plate X on the opposite page 
the outline of the work that is to be completed by the 
student. The dimensions given on this plate are to be used in 
working out the problem, but are not to appear on the finished 
plate. The first figure shown represents a rectangular block with a 
rectangular hole cut through from front to back. The other two 
figures represent the same block in different positions. In drawing 
these figures, the student must put in all construction lines in order 
t<> show how each view is obtained. 

After completing the construction of the views as shown, the 
projection of four holes, \ inch in diameter each, are to be drawn. 
( me hole passes through the center of each end, and one hole through 
the center of each side. All these small holes pass completely 
through to the large hole in the center of the block. Next, put two 
square projecting pieces on the front face of the block, on the center 
line, ] inch from each end. These projecting pieces are to be \ 
inch square and \ inch deep. 

The projections of the four small holes and two projecting 
pieces are to be drawn in all views in the conventional manner, 
■"•d the ry construction lines for this work are to be left 

on the plate and inked in. 



202 



MECHANICAL DRAWING 



137 







l 


5! 






T 

N|cO 


I 










J 










zj\ S \ 

' iJ2^\ \ 














x> 


5 














1 


! 

™ i 
i 

■ 


a-* 




* 


J 


i 












J 

I 
































L 




—j — 


c 




^ 


t 


—$- 






t 

CD 

X 
it 

3 

P 




z 






«« 


c 








J 

~-|eO 

i 

































203 



MECHANICAL DRAWING 

PLATE XI 

At the left of this plate draw the plan, front and side views 
of the monument shown in elevation on reproduced Plate XI on the 
ge. The total height of the monument is 6 inches. 
All four E alike except that the width of the base is 2 inches 

and the depth 1 ) inches, and the width of the body of the monument 
is 1 \ inches and the depth 1 inch. The height of the ba>e i- § inch, 
of body 3 inches, and the faces just above the base have a slope of 
with the horizontal. The width of the ridge at the 
extreme top of the monument is 1 inch. 

The figures for the right side of the plate represent a pen- 
tagonal pyramid in three positions. The first position is the pyramid 
with the axis vertical. The height of the pyramid is 2J inches, 
and the diameter of the circle circumscribed about the base 2h inches. 
The center of the circle is 6 inches from the left margin and 2^ 
inches below the upper border line. Spaces between figures to 
| inch. 

In the second figure the pyramid has been revolved about the 
right-hand corner of the base as an axis, through an angle of 15 
degrees. The axis of the pyramid, shown dot and dash, is therefore 
at 75 degrees. The method of obtaining 75 degrees and 15 degrees 
with the triangles was shown in Part I. From the way in which 
the pyramid has been revolved, all angles with V must remain the 
same as in the fir-t position; hence the vertical projection will be 
the same shape and size as before. All points of the pyramid 
remain the same distance from T~. The points on the plan are 
found on T->quare lines through the corners of the first plan and 
directly above the points in elevation. In the third position the 
pyramid has been swung around, about a vertical line through the 

. as axis, through 30 degrees. The angle with the horizontal 
plane remains the same; consequently the plan is the same size 
and shape as in the second position, but at a different angle. Heights 
of all points of the pyramid have not changed this time, and hence 
are projected across t'r«>m the second elevation. 

PLATE XII 
DEVELOPMENTS 
On this plate draw the developments of a truncated octagonal 
i, and of a truncated pyramid having a square base. The 



204 



MECHANICAL DRAWING 



139 




205 



1 w 



MECHANICAL DRAWING 



arrangement on the plate is left to the student; but it is suggested 
that the truncated prism and its development be placed at the left, 



\ 



I I 
I I 



n 



203. Plan, Elevation, and Development of an Octagonal Prism 

and that the development of the truncated pyramid be placed under 
the development of the prism; the truncated pyramid may be placed 
at the right. 








ation, and Development of a Square Pyramid and Cutting Plane 



I. Plan, Kiev 

The prism and its development are shown in Fig. 203. The 
prism is 3 inches high, and the base is inscribed in a circle 2| inches 
in diameter. The plane forming the truncated prism is passed as 
indicated, the distance AB being 1 inch. Ink a sufficient number 
of construction lines to *how clearly the method of finding the 
development. 



206 



MECHANICAL DRAWING 141 

The pyramid and its development are shown in Fig. 204. Each 
side of the square base is 2 inches, and the altitude is 3| inches. 
The plane forming the truncated pyramid is passed in such a posi- 
tion that AB equals If inches, and AC equals 2\ inches. In this 
figure the development may be drawn in any convenient position, 
but in the case of the prism it is better to draw the development 
as shown. Indicate clearly the construction by inking the con- 
struction lines. 

PLATE XIII 
ISOMETRIC AND OBLIQUE PROJECTION 

In the upper left quarter of this plate draw the isometric pro- 
jection of the block which is shown on reproduced Plate X, page 137, 
taking the dimensions from your finished Plate X. The idea for 
this problem can be obtained by referring to Fig. 158 in this text- 
book. 

In the upper right quarter of this plate draw the isometric 
projections of the two round bolts described in 7 and 8 of Plate IX, 
taking dimensions from your finished Plate IX. 

In the lower half of this plate draw, at 45 degrees, the oblique 
projections of the cylinder and the rectangular block, described in 
9 and 10 of Plate IX, taking dimensions from your finished Plate IX. 
The idea for this can be obtained by referring to Figs. 175 and 179 
in this textbook. 

PLATE XIV 
FREE=HAND LETTERING 

On account of the importance of free-hand lettering, the student 
should practice it at every opportunity. For additional practice, 
and to show the improvement made since completing Part I, lay 
out Plate XIV in the same manner as Plate I, and letter all four 
rectangles. Use the same letters and words as in the lower right- 
hand rectangle of Plate I. 

PLATE XV 
LETTERING 

First lay out Plate XV in the same manner as previous plates. 
After drawing the vertical center line, draw light pencil lines as 



207 






MECHANICAL DRAWING 




208 



MECHANICAL DRAWING 143 

guide lines for the letters. The height of each line of letters is shown 
on the reproduced plate. The distance between the letters should be 
\ inch in every case. The spacing of the letters is left to the student. 
He may facilitate his work by lettering the words on a separate piece 
of paper, and finding the center by measurement or by doubling the 
paper into two equal parts. The styles of letters shown on the 
reproduced plate should be used. 



209 



INDEX 



211 



INDEX 



The page numbers of this volume will be found at the bottom of the pages; 
the numbers at the top refer only to the section. 



Page 



Page 



A 




Blueprints analyzed (continued) 




Angles 108, 


112 


cone gears 


41 


Armature end ring 


50 


cross-feed connecting link 


33 


Armature head 


48 


diamond tool post T bolt 


32 


Armature punchings 


49 


down-feed worm 


43 


Assembled cone gears 


41 


down-feed worm wheel 


28 






drawing-in bolt 


36 


B 




end shield 


47 


Back clutch pinion 


26 


face gear 


42 


Back tool post 


38 


field punchings 


50 


Bevel gears for rolls on sheet bar and 




geared mechanism for loom 


57 


slab-mill steam flying 




gears used on 12-inch merchant 




shear table 


52 


mill 


51 


Binder arm for rope take-up 


55 


globe valve 


40 


Blueprint reading 11 


-65 


intermediate shaft clutch 


30 


analysis of typical blueprints 


24 


knee shaft clutch 


37 


general directions for 


13 


miscellaneous mechanisms for 




introduction 


11 


looms 


58 


Blueprints 


11 


motor coupling for rod mill drive 


54 


importance of 


12 


plan of foundry building 


63 


process of making 


11 


pole piece lamination 


51 


reading 


13 


roof truss 


61 


Blueprints analyzed 


24 


saddle adjusting lever 


44 


armature end ring 


50 


saddle nut 


24 


armature head 


48 


shaft-bearing pedestal 


47 


armature punchings 


49 


shuttle mechanism for loom 


56 


assembled cone gears 


41 


spindle 


60 


back clutch pinion 


26 


swivel table stud 


32 


back tool post 


38 


top pulley bracket 


44 


bevel gears for rolls on sheet bar 




wheel guard T bolt 


32 


and slab-mill steam fly- 




work spindle slide 


35 


ing shear table 


52 


Bow pen and pencil 


79 


binder arm for rope take-up 


55 






center arm head 


39 


C 




center rest assembly 


35 


Center arm head 


39 


center rest base 


34 


Center rest assembly 


35 


center rest top 


33 


Center rest base 


34 


check valve 


58 


Center rest top 


33 



Note. — For page numbers see foot of pages. 



213 



INDEX 







Page 




Page 


k valve 




58 


E 








111 


Ellipse 


117, 169 


i 


7 




End shield 


47 






41 


Epicycloid curve 


120 


115 


174 


175 






• ions 




117 


F 




i atioiifl used in mechanical 




Fact 1 gear 


42 


drawing 




22 


Field punchings 


50 


onnecting link 




33 


Finish lines 


20 


isometrii - 


179, 


182 


First-angle projection 


58, 141 


id curve 




119 






Cycloidal curves 




119 


G 




Cylin 115, 


173, 


183 


Cleared mechanism for loom 


57 


D 






Clears used on 12-inch merchant 






mill 


51 








Geometrical definitions 


107 


Developments <>f sun: 




172 


angles 


108, 112 


cone 




175 


conic sections 


117 


cylinder 

ingular prism 
_ liar triangular pyramid 
right 

nd tool post T bolt 


173, 


177 
174 
176 
174 
32 


lines 

odontoidal curves 

solids 

surfaces 


107 
119 
113 
108 


Dimension lines 




17 


Geometrical problems 


121 


Down-feed worm 
Down-feed worm wheel 




43 

28 


Globe valve 
Ground line 


40 

146 


Drawing-in bolt 




36 


H 




Drawing instruments and mate- 






rials 


6; 


', 88 


Horizontal center line 


15 


I >«:t rn compaae 




82 


Hyperbola 


US 


!•< -aril 




68 


Hypocycloid curve 


120 


bow pen and pencil 




79 






'•(.III; 




76 


I 




dividers 




78 


Inclining of objects 


156 






70 


India ink 


80 


how to hold 




88 


Intermediate shaft clutch 


30 


ink 




80 


Intersections 


22. 164 


irregular curve 




82 


planes with cones or cylinders 169 


paper 




67 


planes with planes 


164 


pen 




79 


Involute curves 


120 


pencils 




69 


Irregular curve 


82 


proti 




81 


Irregular surfaces 


22 






SI 


Isometric projection 


179 


T-square 




7(1 


applications of 


182 


thumb tacks 




69 


blocks 


183 


triai ^ 




72 


box with cover 


184 






18 


cube 


179, 182 


'■ 


Its. 









214 



INDEX 



Page 



Page 



Isometric projection (continued) 






Mechanical drawing (continued) 






cylinder 




183 


oblique projection 




189 


framework 




183 


projections 




139 


house 




183 


surfaces, development of 




172 


prism 




186 


Miscellaneous mechanisms for looms 


58 


pyramid 




186 


Motor coupling for rod mill drive 


54 


K 

Knee shaft clutch 




37 


Objects, representation, rotating, 
inclining of 


and 


155 


L 






Oblique projection 
Odontoidal curves 




189 
119 


Large work, methods of showing 




19 


Orthographic projection 




139 


Lettering 


83, 


194 


development of surfaces 




172 


forming 




83 


ground fine 




146 


inking 




84 


intersections 




164 


penciling 




199 


methods of 




142 


size of letters 




194 

84 


practical problems in 




149 


spacing 




projection fines 




146 


titles for working drawings 




199 


representation of objects 




155 


types of 


85, 


194 


rotating and inclining of objects 


156 


Line problems 




92 


rules of 




147 


Line shading 


20, 


192 


true length of lines 




153 


Lines 16, 20, 


107, 


153 








dimension 




17 


P 






finish 




20 


Parabola 


118, 


,171 


line shading 




20 


Pencils 


69, 79 


section 




18 


Pens 




79 


shade 




20 


Plan of foundry building 




63 


true length of 




153 


Pole piece lamination 




51 


working 




16 


Polygons 
Polyhedrons 




108 
113 


M 






Prisms 113, 


174 


, 186 


Mechanical drawing 11 


,67- 


-209 


Projection lines 




146 


"don'ts" in drafting work 




91 


Projection rules 




147 


drawing instruments, how to hold 


. 88 


Projections 15, 139, 


179 


, 189 


geometrical definitions 




107 


isometric 




179 


geometrical problems 




121 


oblique 




189 


instruments and materials 




67 


orthographic 




139 


intersections 




164 


Protractor 




81 


isometric projection 




179 


Pyramids 114, 


176 


, 186 


lettering 


83, 


194 


Q 






line problems (preliminary) 




92 


Quadrilaterals 




iio- 


line shading 




192 


R 






lines, true length of 




153 






objects, representation, rotating, 




Rectangular hyperbola 




119 


and inclining of 




155 


Representation of objects 




155 



Note. — For page numbers see foot of pages. 



215 



INDEX 





Page 




Page 


Roof ' 


61 


T 




Rotating erf obji 


156 


T-square 


70 


S 




Third-angle projection 


59, 140 




Top pulley bracket 


44 


Saddle adjusting Lever 


44 


Triangles 


109 


Saddle nut 


24 


Triangles (instrument) 


72 


Sea Irs 


81 


True length of lines 


153 


- 


18 






Shade lines 


20 


V 




Shading, line 


20 






Shaft-bearing pedestal 


47 


Vertical center line 


15 


Shuttle mechanism for loom 


56 


Views of object 


13, 139 


Single picture views 


23 






Solids 


113 


W 




Spheres 


116 






Spindle 


60 


Wheel guard T bolt 


32 


Surt': ; 


108 


Work spindle slide 


35 


Swivel table stud 


32 


Working drawings 


11 


Symbols used in mechanical d 


rawing 21 


Working lines 


16 



-for page numbers see foot of pages. 



216 



L 



